A relation y = f(x) is a function if for each value of x there is only value of y. For no value of x can there be more than 1 value of x.

y^9 = x^2 + 5

`y = root(9)(x^2 + 5)`

Here, for any value of x there is only one value of y. `y = root(9)(x^2 + 5)` is a function.

**y^9 = x^2 + 5 is a function.**