Question

Factor the following polynomial completely. -x^2y^2 + x^4 + 9y^2 - 9x^2

Answer 1

move the pure terms to outside

x^4-9x^2-x^2y^2+9y^2
grop
(x^4-x^2y^2)+(-9x^2+9y^2)
undistribute common factors
(x^2)(x^2-y^2)+(-9)(x^2-y^2)
reverse distributive
(x^2-y^2)(x^2-9)
factor perfect squares
(x-y)(x+y)(x-3)(x+3)