Answer
$(x-y)(x+y)(x^2+y^2)$
Work Step by Step
RECALL:
$a^2-b^2=(a-b)(a+b)$
The given expression can be written as:
$(x^2)^2-(y^2)^2$
Factor this expression using the formula above with $a=x^2$ and $b=y^2$ to have:
$=(x^2-y^2)(x^2+y^2)$
Factor the first binomial using the same formula with $a=x$ and $b=y$ to have:
$=(x-y)(x+y)(x^2+y^2)$
