## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$\{x\in \mathbb{R}\ |\ x\neq 5\}$
The domain of a rational expression is the whole set of real numbers, excluding the numbers that yield zero in the denominator. Here, we exclude $x$ for which the denominator is equal to zero. To find the number/s to be excluded, set the denominator equal to zero, then solve the equation: $x-5=0$ $x=5$ Thus, $5$ has to be excluded from the domain. Hence, the domain of the given expression is $\{x\in \mathbb{R}\ |\ x\neq 5\}$.