#### Answer

not factorable

#### Work Step by Step

$\bf{\text{Solution Outline:}}$
The given expression, $
9r^2+100
,$ is prime.
$\bf{\text{Solution Details:}}$
A binomial can be factored if the $GCF$ between its terms is not $1$, or if it is a difference of $2$ squares, or if it is a sum/difference of $2$ cubes.
The $GCF$ of the terms of the given binomial is $1.$ It is also not a differene of two squares because it uses a plus sign between its terms. It is also not a difference of $2$ cubes because its terms are not perfect cubes. Hence, the given expression is $\text{
not factorable
.}$