(x + 2) is a factor of x4 - 16.
x4 - 16 = (x2 - 4) (x2 + 4)........... [using a2−b2 = (a + b)(a - b)]
(x2 - 4) is further factorable using the same formula.
So we get, (x2 - 4) = (x + 2)(x - 2)
This shows that, (x + 2) is a factor of x4 - 16
x - 2 is a factor of x4−2x3+5x2−4x+9
The expression x4+8x2+16 can be factorized as: