2x的平方-x-1=0
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2x的平方-x-1=0
2x的平方-x-1=0
2x的平方-x-1=0
2x^2-x-1=0
(2x+1)(x-1)=0
2x+1=0 x-1=0
x1=-1/2 x2=1
2x^2-x-1=(2x+1)(x-1)=0(十字相乘法)
x=-1/2 x=1
2x²-x-1=0
(2x+1)(x-1)=0
x = -0.5,或者x=1
(2x+1)*(x-1)=0 得 x=-1/2或1
2x²-x-1=0
(2x+1)(x-1)=0
2x+1=0或x-1=0
x=-1/2或x=1
2x²-x-1=0
2(x²-1/2x+1/4)-2×1/4-1=0
2(x-1/2)²=3/2
(x-1/2)²=3/4
x-1/2=±√3/2
x1=1/2+√3/2
x2=1/2-√3/2