Answer
$(y-5)(x+9)$
Work Step by Step
Regroup the terms to obtain:
$=(xy-5x)+(9y-45)$
Factor out the greatest common factor of each group to obtain:
$=x(y-5) + 9(y-5)$
The $GCF$ for the two terms is a binomial, $(y-5)$. Even though it is a binomial, we can factor it out just like we would factor out a number or a variable. Thus, we factor out the binomial to obtain:
$=(y-5)(x+9)$