#### Answer

$u^3(3u-4)$

#### Work Step by Step

Both terms have at least a factor of $u^3$ shared, so that can be factored out. $3$ and $4$ have no shared factors besides $1$, so there isn't anything factored out from those numbers. That means that $u^3$ can only be factored out to get $u^3(3u-4)$, since $u^3(u)=u^4$ upon distribution.