Answer
$(x^2+1)(5x^2-3)$.
Work Step by Step
The given expression is
$=5x^4+2x^2-3$.
We can write
$=5(x^2)^2+2x^2-3$
Substitute $x^2=u$.
$=5(u)^2+2u-3$
Simplify.
$=5u^2+2u-3$
Rewrite $2u$ as $5u-3u$.
$=5u^2+5u-3u-3$
Factor.
$=5u(u+1)-3(u+1)$
$=(u+1)(5u-3)$.
Substitute back $u=x^2$.
$=(x^2+1)(5x^2-3)$.