# How do you factor by grouping 3ax - 3bx - ay + by?

Mar 27, 2018

$\left(a - b\right) \left(3 x - y\right)$

#### Explanation:

$\text{consider the expression as two groups}$

$\left[3 a x - 3 b x\right] + \left[- a y + b y\right]$

$\text{factorise each 'group'}$

$\textcolor{red}{3 x} \left(a - b\right) \textcolor{red}{- y} \left(a - b\right)$

$\text{take out the common factor } \left(a - b\right)$

$\left(a - b\right) \left(\textcolor{red}{3 x - y}\right)$

$\Rightarrow 3 a x - 3 b x - a y + b y = \left(a - b\right) \left(3 x - y\right)$