当前位置:首页 > 七年级 > 数学试卷

【323579】2023七年级数学上册 第3章 一次方程与方程组《一元一次方程的解法(2)》课时作业(

时间:2025-01-15 19:25:27 作者: 字数:3518字
简介:


一元一次方程的解法(2课时)

(30分钟 50)

一、选择题(每小题4,12)

1.下列解方程去分母正确的是 (  )

A. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> -1= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> ,2x-1=3-3x

B. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =-1,2(x-2)-3x-2=-4

C. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> -y,3y+3=2y-3y+1-6y

D. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> -1= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> ,12y-1=5y+20

【解析】选C.A.不含分母的项漏乘各分母的最小公倍数6,错误;

B. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> 的分子作为一个整体去分母后没有加上括号,错误;

C.正确;

D.不含分母的项漏乘各分母的最小公倍数15,错误.

2.解方程 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =7,下列变形较简便的是 (  )

A.方程两边都乘20,4(5x-120)=140

B.方程两边都除以 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> , <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x-30= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a>

C.去括号,x-24=7

D.方程整理, <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> · <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =7

【解析】选C.解方程时,并不一定按照解一元一次方程的步骤去解,根据方程特点选择合适的步骤去解,此题中因为 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> 互为倒数,相乘为1,所以可以直接去括号更为简单.

【变式训练】解方程 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> -2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x怎样变形较简单?

【解析】去中括号, <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x+1+3- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x.

3.我们来定义一种新运算: <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =ad-bc.例如, <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =2×5-3×4=-2;再如 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =3x-2,按照这种定义,对于 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> ,x的值是(  )

A.- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> B.- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> C. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> D. <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a>

【解析】选A.根据运算的规则: <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> 可化简为:2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> -2x=(x-1)-(-4)× <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> ,化简可得-2x=3,x=- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> .

二、填空题(每小题4,12)

4.如果a2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> a2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> 是同类项,m=    .

【解析】由同类项的定义可知, <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (2m+1)= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (m+3),解这个方程得:m=2.

答案:2

5.a=    ,1- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a>  <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> 互为相反数.

【解析】根据题意得1- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> + <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =0,

去分母,6-3(a-1)+2(2a-3)=0,解得a=-3.

答案:-3

【变式训练】当m=    ,代数式 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> m-3的值相等.

【解析】根据题意得 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> m-3,

去分母,3(2m-3)=5×2m-3×15,解得m=9.

答案:9

6.有一系列方程:1个方程是x+ <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =3,解为x=2;2个方程是 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> + <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =5,解为x=6;3个方程是 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> + <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =7,解为x=12;……根据规律,10个方程是       ,其解为    .

【解析】观察给出的方程,10个方程是

 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> + <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =21,其解为x=10×11=110.

答案: <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> + <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =21 x=110

三、解答题(26)

7.(8)解方程:

(1)(2013·梧州中考) <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x+2· <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =8+x.

(2) <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =1.

【解析】(1)原方程变形为 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x+ <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x+2=8+x,

去分母,x+5x+4=16+2x,移项,合并同类项,4x=12,方程两边都除以4,x=3.

【一题多解】原方程变形为 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x+ <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x+2=8+x,

移项,合并同类项,2x=6,

方程两边都除以2,x=3.

(2)原方程变形为 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> =1,

去分母,5(30x-100)-2(40x-80)=10,

去括号,150x-500-80x+160=10,

移项,合并同类项,70x=350,

方程两边都除以70,x=5.

【易错提醒】1.在利用分数的基本性质把分母中的小数化为整数时,方程的右边不变.

2.去分母时等号右边的1不能漏乘.

3.去分母时分子作为一个整体,必须加括号.

8.(8)在解方程3(x+1)- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (x-1)=2(x-1)- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (x+1),我们可以将(x+1),(x-1)各看成一个整体进行移项、合并,得到 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (x+1)= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (x-1),再约分、去分母得3(x+1)=2(x-1),进而求解得x=-5,这种方法叫整体求解法.请用这种方法解方程:

5(2x+3)- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (x-2)=2(x-2)- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (2x+3).

【解析】移项、合并同类项得 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (2x+3)= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (x-2),

约分、去分母,2(2x+3)=x-2,

去括号,4x+6=x-2,

移项、合并同类项,3x=-8,两边都除以3,x=- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> .

【培优训练】

9.(10)规定新运算符号 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> 的运算过程为,a <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> b= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> a- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> b.解方程2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x)=1 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x.

【解析】因为2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x,

所以2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> (2 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x)= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> ,1 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x,

因此原方程可化为: <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> = <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x,

去括号,: <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> + <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x,

移项, <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x+ <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x= <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> - <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> + <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> ,

合并同类项, <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> x=- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> ,

方程两边都除以 <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> ,x=- <a href="/tags/16/" title="课时" class="c1" target="_blank">课时</a> <a href="/tags/55/" title="数学" class="c1" target="_blank">数学</a> <a href="/tags/380/" title="方程" class="c1" target="_blank">方程</a> <a href="/tags/381/" title="作业" class="c1" target="_blank">作业</a> .

4