✔ 最佳答案
x^2y^2 + xy - x^2 - y^2 + x + y + 2
= (- x^2 + x^2 y^2 - y^2 + 1) + (x + xy + y + 1)
= [y^2 (x^2 - 1) - (x^2 - 1)] + [y(x + 1) + (x + 1)]
= (x^2 - 1)(y^2 - 1) + (x + 1)(y + 1)
= (x + 1)(x - 1) (y + 1)(y - 1) + (x + 1)(y + 1)
= (x + 1)(y + 1) [ (x - 1)(y - 1) + 1]
= (x + 1)(y + 1)(xy - x - y + 2)