# How do you factor 15x^2 y^3 + 10x^4 y^8?

$3 \cdot \textcolor{g r e e n}{5 \cdot x \cdot x \cdot y \cdot y \cdot y} + 2 \cdot \textcolor{g r e e n}{5 \cdot x \cdot x} \cdot x \cdot x \cdot \textcolor{g r e e n}{y \cdot y \cdot y} \cdot y \cdot y \cdot y \cdot y \cdot y$
$5 {x}^{2} {y}^{3} \left(3 + 2 {x}^{2} {y}^{5}\right)$
In order to prove you're right, you can resort to the exponential law which states that ${x}^{n} \cdot {x}^{m} = {x}^{n + m}$ and distribute your factor. ;)