find the factors
81=3 times 3 times 3 times 3
336960=2 times 2 times 2 times 2 times 2 times 2 times 3 times 3 times 3 times 3 times 5 times 13
there is a 3 times 3 times 3 times 3 in both numbers (multiplied to get 81) so we divide both numbers by 81
81((x^4)-4160)
that is the factored form