(x+y-xy-1)^2=(x-1)^2(y-1)^2

问题描述:

(x+y-xy-1)^2=(x-1)^2(y-1)^2
(x+y-xy-1)^2这步是怎么变到(x-1)^2(y-1)^2这步的?

(x+y-xy-1)^2
=(x(1-y)-(1-y))^2
=((x-1)(1-y))^2
=(x-1)^2(1-y)^2
=(x-1)^2(y-1)^2