Ah, I forgot. The graphs of an inverse function is the graph of the original function, reflected about the line y = x. So you could also draw a graph of the two functions and determine whether they appear to be relfections about the line y = x.

technically g(x) is not a function as a function only returns one value for a given input. It does not pass the vertical line test and does not qualify as a function. I just drew it that way to illustrate how the reflection works.