Answer
$(3x-5)(3x+5)$
Work Step by Step
The given expression is equivalent to:
\begin{align*}
&=(3x)^2-5^2
\end{align*}
Recall:
$a^2-b^2=(a-b)(a+b)$
Factor the expression using the formula above with $a=3x$ and $b=5$ to obtain:
$$(3x)^2-5^2=(3x-5)(3x+5)$$