Question

Resolve into factors ​

Answer 1

Answer:

(xy-1+x+y)(xy-1-x-y)

Step-by-step explanation:

(x^2 - 1)(y^2 - 1) - 4xy

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

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

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

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