# How do you factor completely 3x^2 - 9x - 30?

Apr 29, 2018

Divide the whole equation by 3 to simplify:

$3 {x}^{2} - 9 x - 30 = {x}^{2} - 3 x - 10$

Find factors of $10$ : $1 , 2 , 5 , 10$):
$2$ and $5$ work to make $10$ and $3$

Therefore,

$\left(x + 2\right) \left(x - 5\right)$

Do not forget to add the three back!

$3 \left(\left(x + 2\right) \left(x - 5\right)\right)$

So you would multiply out the brackets first, then the result should be ${x}^{2} - 3 x - 10$. Multiply all factors out with $3$ and this should give you $3 {x}^{2} - 9 x - 30$