x²+8x-2=0 x²-x-1=0 2x²-5x+1=0 4x²-2x-1=0用配方法解方程!
问题描述:
x²+8x-2=0 x²-x-1=0 2x²-5x+1=0 4x²-2x-1=0
用配方法解方程!
答
x²+8x-2=0
(X+4)²-16-2=0
(X+4)²=18
X=±3√2-4
x²-x-1=0
(X-1/2)²-1/4-1=0
(X-1/2)²=5/4
X=±√5/2+1/2
2x²-5x+1=0
2(X-5/4)²-25/8+1=0
2(X-5/4)²=17/8
X=±√14/4+5/4
4x²-2x-1=0
(2X-1/2)²-1/4-1=0
(2X-1/2)²=5/4
X=±√5/4+1/4