Answer:
C. f-¹(x) = x⁹ is the correct inverse of f(x) = 9x⁸.
To find the inverse of a function, we need to "undo" the equation by reversing the operations performed on the variable.
Since f(x) multiplies its input by 9, then divides it by 8, the inverse of f(x) must divide its input by 9 then multiply it by 8.
Therefore, f-¹(x) = x⁹ is the inverse of f(x) = 9x⁸.