Answer
$-5(4a+3)(4a-3)$
Work Step by Step
Factoring the negative $GCF=
-5
$, the given expression, $
-80a^2+45
,$ is equivalent to
\begin{array}{l}
-5(16a^2-9)
\end{array}
Using $x^2-y^2=(x+y)(x-y)$ or the factoring of the difference of 2 squares, then the factored form of the expression, $
-5(16a^2-9)
,$ is
\begin{array}{l}
-5(4a+3)(4a-3)
\end{array}