题目内容
解方程
130+5x=270 | x-0.3x=21 | x÷![]() | ![]() ![]() | 4x=![]() |
解:(1)130+5x=270,
130+5x-130=270-130,
5x=140,
5x÷5=140÷5,
x=28;
(2)x-0.3x=21,
0.7x=21,
0.7x÷0.7=21÷0.7,
x=30;
(3)x÷
=15,
x÷
×
=15×
,
x=9;
(4)
x=
,
x×
=
×
,
x=
;
(5)4x=
,
4x÷4=
÷4,
x=
.
分析:(1)根据等式的性质,两边同减去130,再同除以5即可;
(2)原式变为0.7x=21,根据等式的性质,两边同除以0.7即可;
(3)根据等式的性质,两边同乘
即可;
(4)根据等式的性质,两边同乘
即可;
(5)根据等式的性质,两边同除以4即可.
点评:在解方程时应根据等式的性质,即等式两边同加上、同减去、同乘上或同除以某一个数(0除外),等式的两边仍相等,同时注意“=”上下要对齐.
130+5x-130=270-130,
5x=140,
5x÷5=140÷5,
x=28;
(2)x-0.3x=21,
0.7x=21,
0.7x÷0.7=21÷0.7,
x=30;
(3)x÷
![](http://thumb.1010pic.com/pic5/latex/14.png)
x÷
![](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=9;
(4)
![](http://thumb.1010pic.com/pic5/latex/1207.png)
![](http://thumb.1010pic.com/pic5/latex/927.png)
![](http://thumb.1010pic.com/pic5/latex/1207.png)
![](http://thumb.1010pic.com/pic5/latex/524.png)
![](http://thumb.1010pic.com/pic5/latex/927.png)
![](http://thumb.1010pic.com/pic5/latex/524.png)
x=
![](http://thumb.1010pic.com/pic5/latex/2587.png)
(5)4x=
![](http://thumb.1010pic.com/pic5/latex/365.png)
4x÷4=
![](http://thumb.1010pic.com/pic5/latex/365.png)
x=
![](http://thumb.1010pic.com/pic5/latex/1302.png)
分析:(1)根据等式的性质,两边同减去130,再同除以5即可;
(2)原式变为0.7x=21,根据等式的性质,两边同除以0.7即可;
(3)根据等式的性质,两边同乘
![](http://thumb.1010pic.com/pic5/latex/14.png)
(4)根据等式的性质,两边同乘
![](http://thumb.1010pic.com/pic5/latex/524.png)
(5)根据等式的性质,两边同除以4即可.
点评:在解方程时应根据等式的性质,即等式两边同加上、同减去、同乘上或同除以某一个数(0除外),等式的两边仍相等,同时注意“=”上下要对齐.
![](http://thumb2018.1010pic.com/images/loading.gif)
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