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【330474】初中数学人教八下期中测试(2)

时间:2025-02-09 11:33:22 作者: 字数:20404字

期中测试(2

一、选择题

1.要使二次根式 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 有意义,字母x的取值必须满足(  )

Ax0 B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> C <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> D <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>


2.下列运算错误的是(  )

A <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> C <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ÷ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> D.(﹣ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2=2


3.下列四组线段中,可以构成直角三角形的是(  )

A1.522.5 B456 C234 D1 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 3



4.若等边ABC的边长为2cm,那么ABC的面积为(  )

A <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> cm2 B2 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> cm2 C3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> cm2 D4cm2


5.若x=﹣3,则 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 等于(  )

A.﹣1 B1 C3 D.﹣3


6.如图,在RtABC中,C=90°DAC上一点,且DA=DB=5,又DAB的面积为10,那么DC的长是(  )

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

A4 B3 C5 D4.5


7.若直角三角形两边分别是34,则第三边是(  )

A5 B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> C5 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> D.无法确定


8.如图,在ABC中,DEF分别为BCACAB边的中点,AHBCHFD=12,则HE等于(  )

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

A24 B12 C6 D8


9.若 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ,则x的值等于(  )

A4 B±2 C2 D±4


10.若 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的整数部分为x,小数部分为y,则 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的值是(  )

A <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> C1 D3


二、填空题

11.已知一直角三角形,两边长为34,则斜边上的中线长为   


12.如图,在ABC中,ACB=90°CDAB边上的中线,若CD=3,则AB=   

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>


13.四边形ABCD中,ADBC,要使四边形ABCD成为平行四边形还需满足的条件是   (横线只需填一个你认为合适的条件即可)


14.若xy为实数,且满足|x﹣3|+ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =0,则( <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2018的值是   


15.已知abcABC的三边长且c=5ab满足关系式 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> +b﹣32=0,则ABC的形状为   三角形.


三、解答题

16.计算:

(1)9 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> +5 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ﹣3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(2)2 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(3) <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2016 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2015


17.若xy为实数,且|x+2|+ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =0,求( <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2011


18.如图,四边形ABCD中,EFGH分别是ABBCCDDA的中点.

求证:四边形EFGH是平行四边形.

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>


19.如图,在RtABC中,C=90°B=60°AB=8,求AC的长.

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>


20.已知如图在平行四边形ABCD中,EF是对角线AC上的两点,且AE=CF,求证:AED=CFB

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>


21.如图,梯形ABCD中,ABCDAC平分BADCEADAB于点E.求证:四边形AECD是菱形.

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>


22.如图,四边形ABCDDEFG都是正方形,连接AECG

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(1)求证:AE=CG

(2)观察图形,猜想AECG之间的位置关系,并证明你的猜想.


23.已知RtABD中,边AB=OB=1ABO=90°

问题探究:

(1)AB为边,在RtABO的右边作正方形ABC,如图(1),则点O与点D的距离为  

(2)AB为边,在RtABO的右边作等边三角形ABC,如图(2),求点O与点C的距离.

问题解决:

(3)若线段DE=1,线段DE的两个端点DE分别在射线OAOB上滑动,以DE为边向外作等边三角形DEF,如图(3),则点O与点F的距离有没有最大值,如果有,求出最大值,如果没有,说明理由.

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

答案

1.要使二次根式 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 有意义,字母x的取值必须满足(  )

Ax0 B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> C <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> D <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【考点】二次根式有意义的条件.

【专题】选择题.

【分析】根据二次根式有意义的条件可得2x+30,再解不等式即可.

【解答】解:由题意得:2x+30

解得:x <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

故选D

【点评】此题主要考查了二次根式有意义的条件,关键是掌握二次根式中的被开方数是非负数.


2.下列运算错误的是(  )

A <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> C <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ÷ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> D.(﹣ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2=2

【考点】二次根式的加减法;二次根式的乘除法.

【专题】选择题.

【分析】根据同类二次根式的合并,二次根式的乘除法则,分别进行各选项的判断即可.

【解答】解:A <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 不是同类二次根式,不能直接合并,故本选项正确;

B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> × <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ,计算正确,故本选项错误;

C <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ÷ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ,计算正确,故本选项错误;

D、(﹣ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2=2,计算正确,故本选项错误;

故选A

【点评】本题考查了二次根式的加减及乘除运算,解答本题的关键是掌握二次根式的加减及乘除法则.


3.下列四组线段中,可以构成直角三角形的是(  )

A1.522.5 B456 C234 D1 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 3

【考点】勾股定理的逆定理.

【专题】选择题.

【分析】根据勾股定理的逆定理求出两小边的平方和和大边的平方,看看是否相等即可.

【解答】解:A1.52+22=2.52,即三角形是直角三角形,故本选项正确;

B42+5262,即三角形不是直角三角形,故本选项错误;

C22+3242,即三角形不是直角三角形,故本选项错误;

D12+ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 232,即三角形不是直角三角形,故本选项错误;

故选A

【点评】本题考查了勾股定理的逆定理的应用,注意:如果一个三角形的两边的平方和等于第三边的平方,那么这个三角形是直角三角形,难度适中.


4.若等边ABC的边长为2cm,那么ABC的面积为(  )

A <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> cm2 B2 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> cm2 C3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> cm2 D4cm2

【考点】勾股定理;等边三角形的性质.

【专题】选择题.

【分析】注意三角形的面积的计算方法,首先要作出三角形的高,根据勾股定理就可求出高的长,三角形的面积就很容易求出.

【解答】解:作出三角形的高,则高是 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ,所以三角形的面积是 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ×2× <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> cm2;故选A

【点评】求高是关键,把三角形转化为解直角三角形问题就很易求出.


5.若x=﹣3,则 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 等于(  )

A.﹣1 B1 C3 D.﹣3

【考点】二次根式的性质.

【专题】选择题.

【分析】x=﹣3时,1+x0 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =﹣1﹣x,再去绝对值.

【解答】解:当x=﹣3时,1+x0

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =|1﹣(﹣1﹣x|

=|2+x|=﹣2﹣x=1.故选B

【点评】本题考查了二次根式的化简方法,关键是根据x的取值,判断算式的符号.


6.如图,在RtABC中,C=90°DAC上一点,且DA=DB=5,又DAB的面积为10,那么DC的长是(  )

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

A4 B3 C5 D4.5

【考点】勾股定理;三角形的面积.

【专题】选择题.

【分析】根据RtABC中,C=90°,可证BCDAB的高,然后利用三角形面积公式求出BC的长,再利用勾股定理即可求出DC的长.

【解答】解:RtABC中,C=90°

BCAC,即BCDAB的高,

∵△DAB的面积为10DA=5

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> DA•BC=10

BC=4

CD= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =3

故选B

【点评】此题主要考查学生对勾股定理和三角形面积的理解和掌握,此题的突破点是利用三角形面积公式求出BC的长.


7.若直角三角形两边分别是34,则第三边是(  )

A5 B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> C5 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> D.无法确定

【考点】勾股定理.

【专题】选择题.

【分析】题干中没有明确指出边长为4的边是直角边还是斜边,所以我们需要分类讨论,(1)边长为4的边为直角边;(2)边长为4的边为斜边.

【解答】解:(1)边长为4的边为直角边,则第三边即为斜边,则第三边的长为: <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =5

(2)边长为4的边为斜边,则第三边即为直角边,则第三边的长为: <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

故第三边的长为5 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> cm

故选C

【点评】本题考查了勾股定理在直角三角形中的灵活运用,考查了分类讨论思想,解题的关键讨论边长为4的边是直角边还是斜边.


8.如图,在ABC中,DEF分别为BCACAB边的中点,AHBCHFD=12,则HE等于(  )

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

A24 B12 C6 D8

【考点】三角形中位线定理;直角三角形斜边上的中线.

【专题】选择题.

【分析】利用三角形中位线定理知DF= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> AC;然后在直角三角形AHC中根据“直角三角形斜边上的中线等于斜边的一半”即可将所求线段EH与已知线段DF联系起来了.

【解答】解:DF分别是ABBC的中点,

DFABC的中位线,

DF= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> AC(三角形中位线定理);

E是线段AC的中点,AHBC

EH= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> AC

EH=DF=12

故选B

【点评】本题综合考查了三角形中位线定理、直角三角形斜边上的中线.三角形的中位线平行于第三边且等于第三边的一半.


9.若 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ,则x的值等于(  )

A4 B±2 C2 D±4

【考点】二次根式的加减法.

【专题】选择题.

【分析】方程左边化成最简二次根式,再解方程.

【解答】解:原方程化为 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =10

合并,得 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =10

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =2,即2x=4x=2.故选C

【点评】同类二次根式是指几个二次根式化简成最简二次根式后,被开方数相同的二次根式.

二次根式的加减运算,先化为最简二次根式,再将被开方数相同的二次根式进行合并.

合并同类二次根式的实质是合并同类二次根式的系数,根指数与被开方数不变.

解无理方程,需要方程两边平方,注意检验算术平方根的结果为非负数.


10.若 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的整数部分为x,小数部分为y,则 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的值是(  )

A <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> B <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> C1 D3

【考点】二次根式的加减法.

【专题】选择题.

【分析】因为 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的整数部分为1,小数部分为 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 1,所以x=1y= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ﹣1,代入计算即可.

【解答】解: <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的整数部分为1,小数部分为 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 1

x=1y= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ﹣1

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 1=1

故选C

【点评】关键是会表示 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的整数部分和小数部分,再二次根式的加减运算,即将被开方数相同的二次根式进行合并.


11.已知一直角三角形,两边长为34,则斜边上的中线长为   

【考点】直角三角形斜边上的中线;勾股定理.

【专题】填空题.

【分析】分为两种情况,当34是直角边时,当4是斜边,3是直角边时,求出斜边,根据直角三角形斜边上中线性质求出即可.

【解答】解:当34是直角边时,斜边为: <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =5

斜边上中线为 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

4是斜边,3是直角边时,

斜边上的中线为2

故答案为: <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2

【点评】本题考查了直角三角形斜边上中线性质和勾股定理的应用,能求出符合的所有情况是解此题的关键.


12.如图,在ABC中,ACB=90°CDAB边上的中线,若CD=3,则AB=   

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【考点】直角三角形斜边上的中线.

【专题】填空题.

【分析】根据直角三角形斜边上的中线等于斜边的一半可得AB=2CD

【解答】解:∵∠ACB=90°CDAB边上的中线,

AB=2CD=2×3=6

故答案为:6

【点评】本题考查了直角三角形斜边上的中线等于斜边的一半的性质,熟记性质是解题的关键.


13.四边形ABCD中,ADBC,要使四边形ABCD成为平行四边形还需满足的条件是   (横线只需填一个你认为合适的条件即可)

【考点】平行四边形的判定.

【专题】填空题.

【分析】在已知一组对边平行的基础上,要判定是平行四边形,则需要增加另一组对边平行,或平行的这组对边相等,或一组对角相等均可.

【解答】解:根据平行四边形的判定方法,知

需要增加的条件是AD=BCABCDA=CB=D

故答案为AD=BC(或ABCD).

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【点评】此题考查了平行四边形的判定,为开放性试题,答案不唯一,要掌握平行四边形的判定方法.

两组对边分别平行的四边形是平行四边形;两组对边分别相等的四边形是平行四边形;一组对边平行且相等的四边形是平行四边形;两组对角相等的四边形是平行四边形;对角线互相平分的四边形是平行四边形.


14.若xy为实数,且满足|x﹣3|+ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =0,则( <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2018的值是   

【考点】二次根式的性质;算术平方根;非负数的性质:绝对值.

【专题】填空题.

【分析】直接利用偶次方的性质以及绝对值的性质得出xy的值,进而得出答案.

【解答】解:|x﹣3|+ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =0

x=3y=﹣3

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2018=(﹣12018=1

故答案为:1

【点评】此题主要考查了偶次方的性质以及绝对值的性质,正确得出xy的值是解题关键.


15.已知abcABC的三边长且c=5ab满足关系式 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> +b﹣32=0,则ABC的形状为   三角形.

【考点】勾股定理的逆定理;非负数的性质:偶次方;非负数的性质:算术平方根.

【专题】填空题.

【分析】根据二次根式和偶次方的非负性求出ab的值,根据勾股定理的逆定理判断即可.

【解答】解: <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> +b﹣32=0

a﹣4=0b﹣3=0

解得:a=4b=3

c=5

a2+b2=c2

∴∠C=90°

ABC是直角三角形,

故答案为:直角.

【点评】本题考查了二次根式的性质,偶次方,勾股定理的逆定理的应用,关键是求出a2+b2=c2


16.计算:

(1)9 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> +5 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ﹣3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(2)2 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(3) <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2016 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2015

【考点】二次根式的混合运算.

【专题】解答题.

【分析】(1)先把各二次根式化为最简二次根式,然后合并即可;

(2)利用二次根式的乘除法则运算;

(3)先利用积的乘方得到原式=[ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> )( <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ]2015 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ),然后利用平方差公式计算.

【解答】解:(1)原式=9 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> +10 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ﹣12 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =7 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(2)原式=2×2×2× <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(3)原式=[ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> )( <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ]2015 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

=5﹣62015 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

=﹣ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

=﹣ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【点评】本题考查了二次根式的计算:先把各二次根式化为最简二次根式,再进行二次根式的乘除运算,然后合并同类二次根式.在二次根式的混合运算中,如能结合题目特点,灵活运用二次根式的性质,选择恰当的解题途径,往往能事半功倍.


17.若xy为实数,且|x+2|+ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =0,求( <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2011

【考点】二次根式的性质;算术平方根;非负数的性质:绝对值.

【专题】解答题.

【分析】根据非负数的性质列式求出xy的值,然后代入代数式进行计算即可得解.

【解答】解:由题意得,x+2=0y﹣2=0

解得,x=﹣2y=2

所以,( <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 2011=(﹣12011=﹣1

【点评】本题考查了非负数的性质:几个非负数的和为0时,这几个非负数都为0


18.如图,四边形ABCD中,EFGH分别是ABBCCDDA的中点.

求证:四边形EFGH是平行四边形.

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【考点】根据边的关系判定平行四边形.

【专题】解答题.

【分析】连接BD,再利用三角形中位线定理可得FGBDFG= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> BDEHBDEH= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> BD.进而得到FGEH,且FG=EH,可根据一组对边平行且相等的四边形是平行四边形证出结论.

【解答】证明:如图,连接BD

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

FG分别是BCCD的中点,

所以FGBDFG= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> BD

EH分别是ABDA的中点.

EHBDEH= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> BD

FGEH,且FG=EH

四边形EFGH是平行四边形.

【点评】此题主要考查了中点四边形,关键是掌握三角形中位线定理,三角形的中位线平行于第三边且等于第三边的一半.


19.如图,在RtABC中,C=90°B=60°AB=8,求AC的长.

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【考点】勾股定理;含30度角的直角三角形.

【专题】解答题.

【分析】RTABC中,利用直角三角形的性质,结合已知条件易求A=30°,进而再利用30°的角所对的直角边等于斜边的一半,易求BC,再利用勾股定理可求AC

【解答】解:如图所示,

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

RTABC中,C=90°B=60°

∴∠A=30°

AB=8

BC=4

AC= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =4 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【点评】本题考查了含30°角的直角三角形的性质、勾股定理的运用,解题的关键是先求出BC


20.已知如图在平行四边形ABCD中,EF是对角线AC上的两点,且AE=CF,求证:AED=CFB

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【考点】平行四边形的性质.

【专题】解答题.

【分析】由四边形ABCD是平行四边形,得到AD=BCADBC,根据平行线的性质得到DAC=BCF,推出ADE≌△BCF,根据全等三角形的性质即可得到结论.

【解答】证明:四边形ABCD是平行四边形,

AD=BCADBC

∴∠DAC=BCF

ADEBCF中, <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

∴△ADE≌△BCF

∴∠AED=CFB

【点评】此题考查了平行四边形的性质以及全等三角形的判定与性质.注意平行四边形的对边平行且相等.


21.如图,梯形ABCD中,ABCDAC平分BADCEADAB于点E.求证:四边形AECD是菱形.

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【考点】菱形的判定;梯形.

【专题】解答题.

【分析】首先证明四边形AECD是平行四边形,再由ABCD,得EAC=DCAAC平分BAD,得DAC=CAE,从而得到ACD=DAC,即AD=DC,有一组邻边相等的平行四边形是菱形.

【解答】证明:ABCDCEAD

四边形AECD是平行四边形.

AC平分BAD

∴∠BAC=DAC

ABCD

∴∠ACD=BAC=DAC

AD=DC

四边形AECD是菱形.

【点评】考查了平行四边形和菱形的判定,比较简单.


22.如图,四边形ABCDDEFG都是正方形,连接AECG

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(1)求证:AE=CG

(2)观察图形,猜想AECG之间的位置关系,并证明你的猜想.

【考点】全等三角形的判定与性质;正方形的性质.

【专题】解答题.

【分析】可以把结论涉及的线段放到ADECDG中,考虑证明全等的条件,又有两个正方形,AD=CDDE=DG,它们的夹角都是ADG加上直角,故夹角相等,可以证明全等;再利用互余关系可以证明AECG

【解答】(1)证明:如图,

AD=CDDE=DGADC=GDE=90°

∵∠CDG=90°+∠ADG=ADE

∴△ADE≌△CDGSAS).

AE=CG

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(2)猜想:AECG

证明:如图,设AECG交点为MADCG交点为N

∵△ADE≌△CDG

∴∠DAE=DCG

∵∠ANM=CND

∴△AMN∽△CDN

∴∠AMN=ADC=90°

AECG

【点评】本题可围绕结论寻找全等三角形,根据正方形的性质找全等的条件,运用全等三角形的性质判定线段相等,垂直关系.


23.已知RtABD中,边AB=OB=1ABO=90°

问题探究:

(1)AB为边,在RtABO的右边作正方形ABC,如图(1),则点O与点D的距离为  

(2)AB为边,在RtABO的右边作等边三角形ABC,如图(2),求点O与点C的距离.

问题解决:

(3)若线段DE=1,线段DE的两个端点DE分别在射线OAOB上滑动,以DE为边向外作等边三角形DEF,如图(3),则点O与点F的距离有没有最大值,如果有,求出最大值,如果没有,说明理由.

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【考点】正方形的性质;矩形的判定定理2

【专题】解答题.

【分析】(1)如图1中,连接OD,在RtODC中,根据OD= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 计算即可.

(2)如图2中,作CEOBECFABF,连接OC.在RtOCE中,根据OC= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 计算即可.

(3)如图3中,当OFDE时,OF的值最大,设OFDEH,在OH上取一点M,使得OM=DM,连接DM.分别求出MHOMFH即可解决问题.

【解答】解:(1)如图1中,连接OD

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

四边形ABCD是正方形,

AB=BC=CD=AD=1C=90°

RtODC中,∵∠C=90°OC=2CD=1

OD= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

故答案为 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(2)如图2中,作CEOBECFABF,连接OC

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

∵∠FBE=E=CFB=90°

四边形BECF是矩形,

BF=CF= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> CF=BE= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

RtOCE中,OC= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

(3)如图3中,当OFDE时,OF的值最大,设OFDEH,在OH上取一点M,使得OM=DM,连接DM

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

FD=FE=DE=1OFDE

DH=HEOD=OEDOH= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> DOE=22.5°

OM=DM

∴∠MOD=MDO=22.5°

∴∠DMH=MDH=45°

DH=HM= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

DM=OM= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

FH= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

OF=OM+MH+FH= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> + <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> = <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

OF的最大值为 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

【点评】本题考查四边形综合题、勾股定理、等边三角形的性质、正方形的性质等知识,教育的关键是学会添加常用辅助线,构造直角三角形解决问题,学会在特殊位置寻找最值问题,属于中考压轴题.