题目内容
求未知数X.
x-
x=12
5x÷0.5=42
:x=
:
.
解:(1)
x-
x=12,
x=12,
x
=12
,
x=24;
(2)5x÷0.5=42,
5x÷0.5×0.5=42×0.5,
5x=21,
5x÷5=21÷5,
x=4
;
(3)
:x=
:
,
x=
,
x=
,
x
=
,
x=1.
分析:(1)先化简方程,再依据等式的性质,方程两边同时除以
求解,
(2)依据等式的性质,方程两边同时乘0.5,再同时除以5求解,
(3)根据比例的基本性质,两内项之积等于两外项之积,化简方程,再依据等式的性质,方程两边同时除以
求解.
点评:本题主要考查学生依据等式的性质以及比例的基本性质解方程的能力.
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/7.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/182079.png)
![](http://thumb.1010pic.com/pic5/latex/182079.png)
x=24;
(2)5x÷0.5=42,
5x÷0.5×0.5=42×0.5,
5x=21,
5x÷5=21÷5,
x=4
![](http://thumb.1010pic.com/pic5/latex/36.png)
(3)
![](http://thumb.1010pic.com/pic5/latex/304.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/13.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/517145.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/163365.png)
![](http://thumb.1010pic.com/pic5/latex/506748.png)
x=1.
分析:(1)先化简方程,再依据等式的性质,方程两边同时除以
![](http://thumb.1010pic.com/pic5/latex/13.png)
(2)依据等式的性质,方程两边同时乘0.5,再同时除以5求解,
(3)根据比例的基本性质,两内项之积等于两外项之积,化简方程,再依据等式的性质,方程两边同时除以
![](http://thumb.1010pic.com/pic5/latex/168.png)
点评:本题主要考查学生依据等式的性质以及比例的基本性质解方程的能力.
![](http://thumb2018.1010pic.com/images/loading.gif)
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