Answer
$-16(y+2)(y-2)$
Work Step by Step
Factoring the negative $GCF=
-16
$ results to $
-16(y^2-4)
$. Using $a^2-b^2=(a+b)(a-b)$ or the factoring of the difference of 2 squares, then,
\begin{array}{l}
-16(y^2-4)
\\=
-16(y+2)(y-2)
.\end{array}