解方程:(1)x²-2x-1=0 (2)y²-6y+6=0 (3)3x²-6x+1=0 (4)5x²=6x+8用配方法
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解方程:(1)x²-2x-1=0 (2)y²-6y+6=0 (3)3x²-6x+1=0 (4)5x²=6x+8用配方法
解方程:(1)x²-2x-1=0 (2)y²-6y+6=0 (3)3x²-6x+1=0 (4)5x²=6x+8
用配方法
解方程:(1)x²-2x-1=0 (2)y²-6y+6=0 (3)3x²-6x+1=0 (4)5x²=6x+8用配方法
(1)x²-2x-1=0
x²-2x+1=2
(x-1)²=2
x=1+√2 x=1-√2
(2)y²-6y+6=0
y²-6y+9=3
(y-3)²=3
y=3+√3 y=3-√3
(3)3x²-6x+1=0
x²-2x=-1/3
x²-2x+1=2/3
(x-1)²=6/9
x=1+√6/3 x=1-√6/3
(4)5x²=6x+8
x²-6x/5=8/5
x²-6x/5+9/25=49/25
(x-3/5)²=49/25
x-3/5=7/5 x-3/5=-7/5
x=2 x=-4/5
(1)x²-2x-1=0 ,因为2^2-4*(-1)>0,所以x无解
y²-6y+6=0 同上,y无解
3x²-6x+1=0 同上,x无解
5x²=6x+8
(5x+4)*(x-2)=0
x=-4/5,x=2