Factorize completely: x4−16x^4 - 16x4−16
(x2−4)(x2+4)(x^2-4)(x^2+4)(x2−4)(x2+4)
(x−2)(x+2)(x2+4)(x-2)(x+2)(x^2+4)(x−2)(x+2)(x2+4)
(x−2)2(x+2)2(x-2)^2(x+2)^2(x−2)2(x+2)2
(x−4)(x+4)(x-4)(x+4)(x−4)(x+4)