#### Answer

$2(5-y)(5+y)$

#### Work Step by Step

RECALL:
A difference of two squares can be factored using the formula:
$a^2-b^2=(a-b)(a+b)$
Factor out the greatest common factor, $2$, to obtain:
$=2(25-y^2)
\\=2(5^2-y^2)$
The binomial is a difference of two squares.
Factor the given difference of two squares using the formula above with $a=5$ and $b=y$ to obtain:
$=2(5-y)(5+y)$