# REX04 Domain of Rational Functions

In the previous video, we have learned to rule out values of a variable in a rational expression. In this video, we are going to learn to find the domain of a rational function. This is very similar to the concept of ruling out values of rational expressions.  Watch the Tagalog math tutorial video above and then answer the exercises below. The complete video playlist of the Sipnayan tutorials on Rational Expressions can be found here.

Practice Exercise

Find the domain of the following rational functions.

1.) $f(x) = \dfrac{x - 9}{x - 3}$

2.) $f(x) = \dfrac{2x + 1}{x^2 + 3x + 2}$.

3.) $g(x) = \dfrac{x^2 - 1}{x}$.

4.) $h(x) = \dfrac{x^2 + 2x}{x^2 - 9}$.

5.) $j(x) = \dfrac{x + 6}{3 - x}$.

1. $\{x|x \neq 3\}$
2. $\{x|x \neq -2, x \neq -1\}$
3. $\{x|x \neq 0 \}$
4. $\{ x|x \neq 3, x \neq -3 \}$
5. $\{ x \neq 3 \}$