题目内容
解方程.
①
-2X=![数学公式](http://thumb.1010pic.com/pic5/latex/96.png)
②x+1.5x=30
③2x÷5=15.
解:(1)
-2X=
,
-2X+2X=
+2X,
-
=
+2X-
,
÷2=2X÷2,
X=
;
(2)x+1.5x=30,
2.5x=30,
2.5x÷2.5=30÷2.5,
x=12;
(3)2x÷5=15,
2x÷5×5=15×5,
2x÷2=75÷2,
x=37.5.
分析:(1)根据等式的性质,在方程两边同时加2X,再减去
,最后除以2求解,
(2)先化简,再根据等式的性质,在方程两边同时除以2.5求解,
(3)根据等式的性质,在方程两边同时乘5,再除以2求解.
点评:本题考查了学生根据等式的性质解方程的能力,注意等号对齐.
![](http://thumb.1010pic.com/pic5/latex/602.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/602.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/602.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/42997.png)
X=
![](http://thumb.1010pic.com/pic5/latex/45758.png)
(2)x+1.5x=30,
2.5x=30,
2.5x÷2.5=30÷2.5,
x=12;
(3)2x÷5=15,
2x÷5×5=15×5,
2x÷2=75÷2,
x=37.5.
分析:(1)根据等式的性质,在方程两边同时加2X,再减去
![](http://thumb.1010pic.com/pic5/latex/96.png)
(2)先化简,再根据等式的性质,在方程两边同时除以2.5求解,
(3)根据等式的性质,在方程两边同时乘5,再除以2求解.
点评:本题考查了学生根据等式的性质解方程的能力,注意等号对齐.
![](http://thumb2018.1010pic.com/images/loading.gif)
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