# How do you factor the expression x ^9 - x ^7 y ^2?

You can first take out the ${x}^{7}$ part, and work from there
$= {x}^{7} \left({x}^{2} - {y}^{2}\right)$
$= {x}^{7} \left(x + y\right) \left(x - y\right)$