Factor: x4−y4x^4 - y^4x4−y4.
(x2+y2)(x+y)(x−y)(x^2 + y^2)(x + y)(x - y)(x2+y2)(x+y)(x−y)
(x2−y2)2(x^2 - y^2)^2(x2−y2)2
(x−y)4(x - y)^4(x−y)4
(x+y)2(x−y)2(x + y)^2(x - y)^2(x+y)2(x−y)2