$(-\infty, -7) \cup (-7, 9) \cup (9, +\infty)$
Work Step by Step
The denominator is not allowed to be equal to zero as division of zero leads to an undefined expression. Look for the real numbers that will make the denominators of the given function equal to zero. These numbers are $-7$ for the first denominator and $9$ for the second denominator. Thus, the value of $x$ can be any real number except $-7$ and $9$. Therefore, the domain is $(-\infty, -7) \cup (-7, 9) \cup (9, +\infty)$.