Which of the following relation is correct

Answer:
Both the equation and its inverse are functions.
Step-by-step explanation:
In order to solve this problem lets first find the inverse of this function. This is done below:
[tex]y = x^2 + 8\\[/tex]
We first swap x and y.
[tex]x = y^2 + 8[/tex]
We now isolate y.
[tex]y^2 = x - 8\\y = \sqrt{x - 8}\\f^{-1}(x) = \sqrt{x - 8}[/tex]
Functions are relations between two groups of numbers, in such a way that one number on the input group must generate a singular answer from the output group. This holds true for both f(x) and its inverse, therefore both are functions.