Factor the following:
x^4-7 x^2-144
x^4-7 x^2-144 = (x^2)^2-7 x^2-144:
(x^2)^2-7 x^2-144
The factors of -144 that sum to -7 are 9 and -16. So, (x^2)^2-7 x^2-144 = (x^2+9) (x^2-16):
(x^2+9) (x^2-16)
x^2-16 = x^2-4^2:
(x^2+9) (x^2-4^2)
Factor the difference of two squares. x^2-4^2 = (x-4) (x+4):
Answer: |(x-4) (x+4) (x^2+9)
