Inverse Functions

If f has an inverse, then its graph will be the reflection of the graph of f over the line y = x. The graph of f and its reflection over y = x are drawn below.

*Note: The reflected graph does not pass the vertical line test, so it is not the graph of a function.
Therefore, the function y = x² does not have an inverse function.

The reflection of the graph is an inverse relation, but it is not a function.