Answer
$(x-4)(x-9)$
Work Step by Step
Using the factoring of trinomials in the form $x^2+bx+c,$ the $\text{
expression
}$
\begin{align*}
x^2-13x+36
\end{align*} has $c=
36
$ and $b=
-13
.$
The two numbers with a product of $c$ and a sum of $b$ are $\left\{
-4,-9
\right\}.$ Using these two numbers, the factored form of the $\text{
expression
}$ above is
\begin{align*}
&
(x-4)(x-9)
\end{align*}