用配方法解方程.1.x²-4x+1=0 2.2y²=5y-4 3.x²+4x-2=0 4.2x²-7x+6=0

用配方法解方程.1.x²-4x+1=0 2.2y²=5y-4 3.x²+4x-2=0 4.2x²-7x+6=0

1.x²-4x+1=0
x²-4x=-1
x²-4x+4=3
(x-2)²=3
x-2=±√3
x=2+√3 x=2-√3
2.2y²=5y-4
y²-5y/2=-2
y²-5y/2+25/16=-7/16
(y-5/4)²=-7/16
无解
3.x²+4x-2=0
x²+4x+4=6
(x+2)²=6
x=-2+√6 x=-2-√6
4.2x²-7x+6=0
x²-7x/2+49/16=1/16
(x-7/4)²=1/16
x=7/4+1/4 x=7/4-1/4
x=2 x=3/2