题目内容
求未知数x.
①12:
=x:
②6+1.5x=15 ③x-
x=
.
解:
①12:
=x:
,
x=12×
,
x=6,
x÷
=6÷
,
x=10;
②6+1.5x=15,
6+1.5x-6=15-6,
1.5x=9,
1.5x÷1.5=9÷1.5,
x=6;
③x-
x=
,
x=
,
x÷
=
÷
,
x=
.
分析:①根据比例的基本性质,两内项之积等于两外项之积,把原式改写成
x=12×
,然后等式的两边同时除以
即可;
②等式的两边同时减去6,然后等式的两边再同时除以1.5即可;
③先计算x-
x=
x,然后等式的两边同时除以
即可.
点评:本题主要考查解比例和解方程,根据比例的基本性质和等式的性质进行解答即可.
①12:
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
x=10;
②6+1.5x=15,
6+1.5x-6=15-6,
1.5x=9,
1.5x÷1.5=9÷1.5,
x=6;
③x-
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
![](http://thumb.1010pic.com/pic5/latex/597.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
x=
![](http://thumb.1010pic.com/pic5/latex/13.png)
分析:①根据比例的基本性质,两内项之积等于两外项之积,把原式改写成
![](http://thumb.1010pic.com/pic5/latex/14.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/14.png)
②等式的两边同时减去6,然后等式的两边再同时除以1.5即可;
③先计算x-
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
点评:本题主要考查解比例和解方程,根据比例的基本性质和等式的性质进行解答即可.
![](http://thumb2018.1010pic.com/images/loading.gif)
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