Answer: [tex](-\infty, -8) \cup (-8, \infty)[/tex]
Step-by-step explanation:
I'm assuming you meant [tex]f(x)=\frac{x-9}{x+8}[/tex]
For this function, we need to make sure the denominator is not equal to 0, because if it was, then the fraction would be undefined.
Thus, [tex]x+8 \neq 0 \longrightarrow x \neq -8[/tex]
In interval notation, this is [tex](-\infty, -8) \cup (-8, \infty)[/tex]
