What is the sum of all real numbers x that are not in the domain of the function
f(x) = 1/(x^2 - 7) + 1/(x^4 - 8) + 1/(x^5 - 9)?
The numbers that aren't in the domain of that function are \(\sqrt 7\), \(\sqrt[4]8\), the opposites of both of those, and \(\sqrt[5]9\).
The first two are cancelled out by their opposites, so the answer is \(\sqrt[5]9\).