# How do you factor 12a^2 - 4ac + 3ab - bc?

$12 {a}^{2} - 4 a c + 3 a b - b c = \left(12 {a}^{2} - 4 a c\right) + \left(3 a b - b c\right)$
$= \left(4 a \cdot 3 a - 4 a \cdot c\right) + \left(b \cdot 3 a - b \cdot c\right)$
$= 4 a \left(3 a - c\right) + b \left(3 a - c\right)$
$= \left(4 a + b\right) \left(3 a - c\right)$