Here's the question you clicked on:
Mcwallisch
Does anyone know about composite functions? For what types of functions will (g of f)(x) and (f of g)(x) both equal x? Please explain!
Only inverse functions have those properties.
And really, that's all that needs to be said. Additionally, you would show this by providing an example. And if you want to make sure your explanation is complete, you would provide the definition of an inverse function.