## Elementary Algebra

The domain of the function is the set of all real numbers except $5$.
When the question asks for the domain of the function, it is asking for what values of x can be legally substituted into the function. (For instance, in the function $\frac{2}{x}$, x $\ne$ 0, for this would make the denominator of the fraction equal to 0.) In the given function, $x$ can be substituted by any real number except $5$. When $x$ replaced by $5$, the denominator becomes 0, making the function undefined. Thus, the domain of the function is the set of all real numbers except $5$.