Question

How do you factor completely $x^2-7x+18$?

Answer 1

The given expression does not factor. Maybe these were meant?
$x^2-7x-18=(x+9)(x-2)$

Explanation:
This expression does not factor in- there might be a typo perhaps?
The following are possibly what was meant?
$x^2-7x-18$
Factors of $18$ which subtract to make $7$, are $9$ and $2$.
$x^2-7x-18=(x+9)(x-2)$