Answer
$6(x-y)(x+y)$
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, $6$, to obtain:
$=6(x^2-y^2)$
The binomial is a difference of two squares.
Factor the given difference of two squares using the formula above with $a=x$ and $b=y$ to obtain:
$=6(x-y)(x+y)$