Answer
$(m^{2}-5)(m^{2}+3)$
Work Step by Step
Substitute $u=m^{2}.$
$m^{4}-3m^{2}-10=u^{2}-3u-10=...$
When factoring $x^{2}+bx+c$, we search for factors of $c$ whose sum is $b,$
Here, these factors are $-5$ and $+3$
$...=(u-5)(u+3)$
... bring back m
$=(m^{2}-5)(m^{2}+3)$
