# How do you factor 9z^2 + 27z -az - 3a?

May 8, 2015

We can factor this expression by making groups of 2 terms:

$\left(9 {z}^{2} + 27 z\right) - \left(a z + 3 a\right)$

$9 z$ is common to both the terms in the first group, and $a$ is common to both the terms in the second group

$= 9 z \left(z + 3\right) - a \left(z + 3\right)$

$z + 3$ is common to both the terms now

= color(green)((z+3)(9z-a)