How do you factor completely 15a^2y-30ay?

Sep 2, 2016

$15 {a}^{2} y - 30 a y = 15 a y \left(a - 2\right)$
Both of the terms are divisible by $15$, $a$ and $y$, so by $15 a y$.
$15 {a}^{2} y - 30 a y = 15 a y \cdot a - 15 a y \cdot 2 = 15 a y \left(a - 2\right)$