Answer
none
Work Step by Step
RECALL:
The denominator of a rational expression is not allowed to be equal to zero since division of zero is undefined.
Note that for any real number, the value of $x^2$ will always be zero or higher.
This means that the value of $x^2+9$ is 9 or higher.
Since the value of the denominator will never be zero, the value of $x$ can be any real number.
Thus, no value of the variable will be excluded from its domain.
