#### Answer

$(xy-1)(xy+1)$

#### Work Step by Step

RECALL:
A difference of two squares can be factored using the formula:
$a^2-b^2=(a-b)(a+b)$
The given binomial can be written as:
$=(xy)^2-(1)^2$
This binomial is a difference of two squares.
Factor the given difference of two squares using the formula above with $a=xy$ and $b=1$ to obtain:
$=(xy-1)(xy+1)$