#### Answer

$(x-y-3)(x+y-3)$

#### 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 the given difference of two squares using the formula above with $a=x-3$ and $b=y$ to obtain:
$=[(x-3)-y][(x-3)+y]
\\=(x-3-y)(x-3+y)
\\=(x-y-3)(x+y-3)$