## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$6(y+8)(y-5)$
Factoring the $GCF= 6$, then the given expression, $6y^2+18y-240$ is equivalent to \begin{array}{l} 6(y^2+3y-40) .\end{array} The two numbers whose product is $ac= 1(-40)=-40$ and whose sum is $b= 3$ are $\{ 8,-5 \}$. Using these two numbers to decompose the middle term of the trinomial above, then the complete factored form is \begin{array}{l} 6(y^2+8y-5y-40) \\\\= 6[(y^2+8y)-(5y+40)] \\\\= 6[y(y+8)-5(y+8)] \\\\= 6[(y+8)(y-5)] \\\\= 6(y+8)(y-5) .\end{array}