题目内容
解方程
![数学公式](http://thumb.1010pic.com/pic5/latex/157706.png)
![数学公式](http://thumb.1010pic.com/pic5/latex/157707.png)
x-30%x=49.
解:(1)x
-
=
,
x
-
+
=
+
,
x
×
=1×
,
x=
;
(2)
:0.25=x:1.5,
0.25x=
×1.5,
0.25x÷0.25=0.5÷0.25,
x=2;
(3)x-30%x=49,
70%x=49,
70%x÷70%=49÷70%,
x=70.
分析:(1)依据等式的性质,方程两边同时加
,再同时乘
求解,
(2)先根据比例基本性质,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0.25求解,
(3)先化简方程,再依据等式的性质,方程两边同时除以70%求解.
点评:本题主要考查学生依据等式的性质,以及比例基本性质解方程的能力.
![](http://thumb.1010pic.com/pic5/latex/163365.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
x
![](http://thumb.1010pic.com/pic5/latex/163365.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/365.png)
![](http://thumb.1010pic.com/pic5/latex/96.png)
x
![](http://thumb.1010pic.com/pic5/latex/163365.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
x=
![](http://thumb.1010pic.com/pic5/latex/168.png)
(2)
![](http://thumb.1010pic.com/pic5/latex/8.png)
0.25x=
![](http://thumb.1010pic.com/pic5/latex/8.png)
0.25x÷0.25=0.5÷0.25,
x=2;
(3)x-30%x=49,
70%x=49,
70%x÷70%=49÷70%,
x=70.
分析:(1)依据等式的性质,方程两边同时加
![](http://thumb.1010pic.com/pic5/latex/96.png)
![](http://thumb.1010pic.com/pic5/latex/168.png)
(2)先根据比例基本性质,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0.25求解,
(3)先化简方程,再依据等式的性质,方程两边同时除以70%求解.
点评:本题主要考查学生依据等式的性质,以及比例基本性质解方程的能力.
![](http://thumb2018.1010pic.com/images/loading.gif)
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