## Precalculus (6th Edition)

$\color{blue}{(3a+4)(3a-4)}$
Note that $9a^2=(3a)^2$ and $16=4^2$. Thus, the given binomial is equivalent to: $=(3a)^2-4^2$ Factor using the formula $a^2-b^2=(a+b)(a-b)$ where $a=3a$ and $b=4$ to obtain: $=\color{blue}{(3a+4)(3a-4)}$