Answer
$y^2-16$.
Work Step by Step
The given expression is
$=(-y+4)(-y-4)$
Factor out $-1$.
$=-1(-y+4)(y+4)$
Use distributive property.
$=(y-4)(y+4)$
Use sum and difference pattern $(a-b)(a+b)=a^2-b^2$.
We have $a=y$ and $b=4$.
$=(y)^2-(4)^2$
Simplify.
$=y^2-16$
Hence, the product is $y^2-16$.
