## Algebra 1: Common Core (15th Edition)

$4(2x+1)(x-5)$
$8x^{2}-36x-20$ ...factor out the GCF. $=4(2x^{2}-9x-5)$ ...factor $(2x^{2}-9x-5)$. $ac=-10,\ b=-9$, find factors of $-10$ with a sum of $-9$. $\left[\begin{array}{lllll} \text{Factors of -10 } & \text{Sum of factors} & & & \\ 1\text{ and }-10 & -9 & \text{...what we need}\\ 2\text{ and }-5 & -3 & & & \\ -2\text{ and }5 & 3 & & & \end{array}\right]$ $4(2x^{2}-9x-5)$ ...use the found factors to rewrite $bx$. $=4(2x^{2}+x-10x-5)$ ...factor out the GCF. $=4[x(2x+1)-5(2x+1)]$ ...use the Distributive Property to finish factoring. $=4(2x+1)(x-5)$