Answer
$(y+1)(9y+4)$
Work Step by Step
$9y^{2}+13y+4$
Two factors of $ac=36$, whose sum is $b=13$
are $9$ and $4$.
Rewrite $13y$ as $9y+4y$ and factor in pairs.
$9y^{2}+13y+4$
$=9y^{2}+9y+4y+4\qquad$...factor from each group if possible.
$=9y(y+1)+4(y+1)\qquad$...factor out the common binomial factor,$y+1$.
$=(y+1)(9y+4)$
