Answer:
[tex] \underline{{x}^{4} - 17 {x}^{2} + 16} \\ {x}^{4} - {x}^{2} - 16 {x}^{2} + 16 \\ {x}^{2} ( {x}^{2} - 1) - 16( {x}^{2} - 1) \\ ( {x}^{2} - 1)( {x}^{2} - 16) \\ \boxed{(x - 1)(x + 1)( x - 4)(x + 4)}✓[/tex]
(x-1)(x+1)(x-4)(x+4) is the right answer.
