## Precalculus (6th Edition) Blitzer

$5y^2(2y+3)(2y-3)$
$20y^4 - 45y^2$ factor out GCF... $5y^2(4y^2-9)$ Recall that $a^2−b^2=(a+b)(a−b)$. We use this to simplify the expression: $5y^2(4y^2-9)=5y^2(2y+3)(2y-3)$