Question

Factor the following polynomial completely.

-x2y2 + x4 + 9y2 - 9x2

Answer 1

= x^4 - 9 x^2 - x^2y^2 + 9y^2
= x^2(x^2 - 9) - y^2(x^2 - 9)
= (x^2 - 9)(x^2 - y^2)
= (x-3)(x+3)(x-y)(x+y)