作业帮(2x-7)(2x-7)-(x+1)(x+1)=0用配方法
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(2x-7)(2x-7)-(x+1)(x+1)=0用配方法
(2x-7)(2x-7)-(x+1)(x+1)=0
用配方法
(2x-7)(2x-7)-(x+1)(x+1)=0用配方法
用配方法解方程(2x-7)(2x-7)-(x+1)(x+1)=0
这种题目最好是不用配方法,因为：
(2x-7)(2x-7)-(x+1)(x+1)=(2x-7)²-(x+1)²=[(2x-7)+(x+1)][(2x-7)-(x+1)]
=(3x-6)(x-8)=0,故x₁=2,x₂=8.
一定要用配方法,当然也可以,那就这么作：
(2x-7)(2x-7)-(x+1)(x+1)=(4x²-28x+49)-(x²+2x+1)=3x²-30x+48
=3(x²-10x+16)=3[(x-5)²-25+16]=3[(x-5)²-9]=0
故得(x-5)²=9,x-5=±3,x₁=5-3=2；x₂=5+3=8.
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