Answer
$\displaystyle \frac{1}{x+4},\qquad\frac{x^{2}+1}{x+4}...$
(sample answers)
Work Step by Step
A rational expression is undefined at any value that produces a denominator of 0.
So, place a polynomial such as $(x+4)$ as a factor of the denominator....
$\displaystyle \frac{1}{x+4},\qquad\frac{x^{2}+1}{x+4}...$
(sample answers)