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【330449】初中数学青岛八下第7章测试卷

时间:2025-02-09 11:18:34 作者: 字数:5578字

单元测试卷

一、选择题

1.下列说法中,不正确的是( ).

A 3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的算术平方根 B±3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的平方根

C 3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的算术平方根 D.3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的立方根

2. -1.414  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> π3.142+ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 3.212212221…,这些数中,无理数的个数为( ).

A.5 B.2 C.3 D.4

3. 已知下列结论:①在数轴上的点只能表示无理数;②任何一个无理数都能用数轴上的点表示;③实数与数轴上的点一一对应;④有理数有无限个,无理数有有限个.其中正确的结论是( ).

A.①② B.②③ C.③④ D.②③④

4.  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ,则 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ( )

A <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 8 B±8 C±2 D±8±2

5. 已知一个直角三角形的两边长分别为34,则第三边长是(  )

A5 B25 C <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> D5 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

6. ab为实数,且满足│a2│+ <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =0,则ba的值为( )

A2 B0 C.-2 D.以上都不对

7. 2m-43m-1是同一个数的平方根,则m的值是( )

A-3 B1 C-31 D-1

8.以下列各组数为边的三角形中,是直角三角形的有( )

1345;(2 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ;(332425240.030.040.05

A1B2C3D4

9. 已知Rt△ABC中,∠C=90°,若a+b=14cmc=10cm,则Rt△ABC的面积是(  )

A. 24cm2 B. 36cm2 C. 48cm2 D. 60cm2

10一架25分米长的梯子,斜立在一竖直的墙上,这时梯足距离墙底端7分米.如果梯子的顶端沿墙下滑4分米,那么梯足将滑动(     ) 

 A. 9分米    B. 15分米    C. 5分米     D. 8分米

11.放学以后,小红和小莹从学校分手,分别沿东南方向和西南方向回家,若小红和小莹行走的速度都是40/分,小红用15分钟到家,小莹用20分钟到家,则小红和小莹家的直线距离为( )

A600B. 800C. 1000D. 不能确定

12. △ABC中,AB15AC13,高AD12,则△ABC的周长为(   ) 

A42    B32   C42 或 32   D37 或 33


二、填空题

13.  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的平方根是  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的立方根是

14在数轴上表示 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的点离原点的距离是 , 1 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的相反数是______,绝对值是______

15若一个数的立方根等于它的算术平方根,则这个数是

16直角三角形两直角边长分别为512,则它斜边上的高为_______

17等腰三角形的腰长为5,底边长为8,则它底边上的高为_____,面积为_ ___

1 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 8.如图,小莹用一张长方形纸片ABCD进行折纸,已知该纸片宽AB8cmBC10cm.当小莹折叠时,顶点D落在BC边上的点F处(折痕为AE).则此时EC= 





19.有一长、宽、高分别为5cm4cm3cm的木箱,在它里面放入一根细木条(木条的粗细、形变忽略不计),要求木条不能露出木箱,请你算一算,能放入的细木条的最大长度是_________cm

20. 如图7,已知在 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 中, <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ,分别以 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 为直径作半圆,面积分别记为 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ,则 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的值等于

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>




三、解答题

22.求x值(每题4分,共8分)

(1) <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>




23.计算:(每题4分,共8分)

1  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>





24化简 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>







25阅读下列解题过程:已知abc为△ABC的三边,且满足a2c2b2c2=a4b4,试判断△ABC的形状.

解:∵a2c2b2c2=a4b4(A)∴c2(a2b2)=(a2+b2)(a2b2)(B)∴c2=a2+b2,(C)∴△ABC是直角三角形.

问:①上述解题 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 过程是从哪一步开始出现错误的?请写出该步的代号_______

错误的原因是 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> ______________

本题的正确结论是_________ _.




26请在同一个数轴上用尺规作出  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 的对应的点.





 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>




27.一个直角三角形的两边mn恰好满足等式m- <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> =8,求第三条边的长.











28. 如图,铁路上AB两点相距25km, CD为两村庄,若DA=10km,CB=15kmDA⊥ABACB⊥ABB,现要在AB上建一个中转站E,使得CD两村到E站的距离相等.

DrawObject1 E应建在距A多远处?











29. 已知正方形ABCD的边长为4EAB中点,FA上的一点,且AF= <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> AD

试判断△EFC的形状. 并说明理由

答案解析

一、1- 6 C D B D C C 7-12 B B A D C C

二、13.±2 -2 14.  <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</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/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> -1 15.01 16.60/13

17.312 18.3 cm 19. 5 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 20.2π

DrawObject222.1x=±7.5 (2)x=1/8

23. (1) 3 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> -2 (2)-9

2 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a> 4. 2 -4

25.1(B) (2)等式的两边都除以不为零的数或整式,所得式子才成立

3ABC是直角三角形或等腰三角形.

26.


27.由已知,得2n-12=12-2n=0.

n=6 , m=8

第三边的长为10


28.设E应建在距Ax km,处,根据勾股定理得

102+x2=(25-x)2+152 解得x=15

 <a href="/tags/4/" title="测试" class="c1" target="_blank">测试</a> <a href="/tags/54/" title="试卷" class="c1" target="_blank">试卷</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/1067/" title="青岛" class="c1" target="_blank">青岛</a> <a href="/tags/1078/" title="初中" class="c1" target="_blank">初中</a>

29. △EFC为直角三角形。

根据勾股定理计算得:EF2=5EC2=20CF2=25

∵EF2+ EC2= CF2

∴△EFC为直角三角形