# How do you factor -s^6 + 16s^4?

$- {s}^{6} + 16 {s}^{4} = - {s}^{4} \left({s}^{2} - 16\right) = - {s}^{4} \left({s}^{2} - {4}^{2}\right)$
$= - {s}^{4} \left(s - 4\right) \left(s + 4\right)$
${a}^{2} - {b}^{2} = \left(a - b\right) \left(a + b\right)$