#### Answer

Example 1: $f(x)=\frac{x+5}{x^2+8}$
Example 2: $f(x)=\frac{x+1}{x-15}$

#### Work Step by Step

Example 1: make sure that the denominator is different than $0$ for any $x$ in the set of real numbers.
Example 2: make sure that the denominator is equal to $0$ when $x=15$