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

$3y(y+10)(y-10)$
$3y^{3}-300y\qquad$..factor out $3y$. $=3y(y^{2}-100)\qquad$..Recognize $A^{2}-B^{2}$ in the parentheses: $=3y(y+10)(y-10)$