x^2-2x+|y-1|=2x-4
x^2-4x+4+|y-1|=0
(x-2)^2+|y-1|=0
两个非负的数相加等于0,两个都必须是0,
x-2=0 y-1=0
x=2 y=1
1/x^2-1/y^2=1/4-1/1=-3/4