用配方法计算:x^2+3x+2=0;-x^2+5x+6=0;x^2-6x=-8-学生作业帮-兵器谱
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用配方法计算:x^2+3x+2=0;-x^2+5x+6=0;x^2-6x=-8

来源:学生作业帮 编辑:作业帮 时间:2019/05/24 21:09:59

用配方法计算:x^2+3x+2=0;-x^2+5x+6=0;x^2-6x=-8

你好,zdkjjka
x²+3x+2=0
x²+3x+9/4-1/4=0
(x+3/2)²=1/4
x+3/2=±1/2
x=±1/2-3/2
∴x1=-1,x2=-2

-x²+5x+6=0
x²-5x-6=0
x²-5x+25/4-49/4=0
(x-5/2)²=49/4
x-5/2=±7/2
x=±7/2+5/2
∴x1=6,x2=-1
x²-6x=-8
x²-6x+8=0
x²-6x+9-1=0
(x-3)²=1
x-3=±1
x=±1+3
∴x1=4,x2=2

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