# How do you factor 15abc^2 + 6a^2bc - 6ab + 3bc?

Answer: $3 a b c \left(5 c + 2 a\right) - 3 b \left(2 a + 3 c\right)$
1. See it as $x - y$
$x = 15 a b {c}^{2} + 6 {a}^{2} b c$
$y = \left(6 a b + 3 b c\right)$
So, $\left(15 a b {c}^{2} + 6 {a}^{2} b c\right) - \left(6 a b + 3 b c\right)$
2. Factorise the common factor, $\left(15 a b {c}^{2} + 6 {a}^{2} b c\right) = 3 a b c \left(5 c + 2 a\right)$
$\left(6 a b + 3 b c\right) = 3 b \left(2 a + 3 c\right)$