xy-1+x-y 十字相乘法因式分解
问题描述：
xy-1+x-y 十字相乘法因式分解
怎么做啊
xy-1+x-yx2y-3xy-2x+63x2+4xy+y2
答
xy-1+x-y
=x(y+1)-(y+1)
=(y+1)(x-1)
x2y-3xy-2x+6
=xy(x-3)-2(x-3)
=(x-3)(xy-2)
3x2+4xy+y2
=(3x+y)(x+y)