Factor completely: x4−81x^4 - 81x4−81.
(x2−9)2(x^2 - 9)^2(x2−9)2
(x2−81)(x2+1)(x^2 - 81)(x^2 + 1)(x2−81)(x2+1)
(x2−9)(x2+9)=(x−3)(x+3)(x2+9)(x^2 - 9)(x^2 + 9) = (x-3)(x+3)(x^2+9)(x2−9)(x2+9)=(x−3)(x+3)(x2+9)
(x−3)4(x - 3)^4(x−3)4