{x}^(4) - 17x ^(2) + 16 factor completely​

Question

`{x}^(4) - 17x ^(2) + 16`
factor completely​

Answer 1

`\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)}✓`

(x-1)(x+1)(x-4)(x+4) is the right answer.