(x + y)^2 * (x + y)^2
(x + y)^2 = x^2 +2xy + y^2
(x + y)^2
(x + y)^2 * (x + y)^2 = x^2 + 2xy + y^2
(x - y)^2 * (x - y)^2
(x - y)^2 = x^2 - 2xy + y^2
(x - y)^2
(x - y)^2 * (x - y)^2 = x^2 - 2xy + y^2
(x + y)(x - y)
x^2 - y^2 OR something^2 - another^2