# How do you factor xy³ - 49xyz²?

Both terms have $x$ and $y$ as common factors, so $x {y}^{3} - 49 x y {z}^{2} = x y \left({y}^{2} - 49 {z}^{2}\right)$. But ${y}^{2} - 49 {z}^{2}$ is the difference of two squares. The final answer is:
$x {y}^{3} - 49 x y {z}^{2} = x y \left(y - 7 z\right) \left(y + 7 z\right)$