Answer
$9(r-5)(r+1)$.
Work Step by Step
The given polynomial is
$=9r^2-36r-45$
Factor out $9$.
$=9(r^2-4r-5)$
Rewrite $-4r$ as $-5r+r$.
$=9(r^2-5r+r-5)$
Group the terms.
$=9[(r^2-5r)+(r-5)]$
Factor each group.
$=9[r(r-5)+1(r-5)]$
Factor out $(r-5)$.
$=9(r-5)(r+1)$
Hence, the factor of the polynomial is $9(r-5)(r+1)$.
