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用13m的铁丝网围成一个长边靠墙面积为20m2的长方形,求这个长方形的长和宽,设...
用13m的铁丝网围成一个长边靠墙面积为20m
2的长方形,求这个长方形的长和宽,设平行于墙的一边为xm,可得方程( )
A.x(13-x)=20
B.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000732251432320/SYS201311030007322514323004_ST/0.png)
C.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000732251432320/SYS201311030007322514323004_ST/1.png)
D.
![manfen5.com 满分网](http://img.manfen5.com/res/CZSX/web/STSource/20131103000732251432320/SYS201311030007322514323004_ST/2.png)
考点分析:
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对于一元一次方程ax
2+bx+c=0(a≠0)的两根为x
1,x
2,根据一元二次方程的解的概念知:ax
2+bx+c=a(x-x
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2)这样我们可以在实数范围内分解因式.
例:分解因式2x
2+2x-1
【解析】
∵2x
2+2x-1=0的根为
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即
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,
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∴
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=
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试仿照上例在实数范围内分解因式:
3x
2-5x+1.
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