#### Answer

$3x^2(x+15)(x+3)$

#### Work Step by Step

All terms are divisible by $3x^2$, so factor out $3x^2$ to obtain:
$=3x^2(x^2+18x+45)$
Factor the trinomial. Look for factors of $45$ whose sum is $18$. These factors are $15$ and $3$.
This means that the trinomial can be factored as $(x+15)(x+3)$.
Thus, the completely factored form of the given polynomial is:
$=3x^2(x+15)(x+3)$