Answer
$(9z+4)(5z^{2} + 1)$
Work Step by Step
$45z^{3} + 20z^{2} + 9z + 4$
Factor by grouping, group the first two terms and last two terms together.
$(45z^{3} + 20z^{2}) + (9z + 4)$
Factor out the common factors from both parenthesis.
$5z^{2}(9z+4) + 1(9z+4)$
We take $(9z+4)$ and factor it out which gives us.
$(9z+4)(5z^{2} + 1)$
