分解因式:1-x2-y2+x2y2-4xy=_.

问题描述:

分解因式:1-x2-y2+x2y2-4xy=______.

1-x2-y2+x2y2-4xy
=(1+x2y2-2xy)-(x2+y2+2xy)
=(1-xy)2-(x+y)2
=(1-xy+x+y)(1-xy-x-y).
故答案为:(1-xy+x+y)(1-xy-x-y).