Im confused college pre calc

Question

Give an example of two functions f and g where f g(x) = x for all x in the domain of g, but g f(x) , x for all x in the domain of f

Answer 1

y = x <--- identity line and is it's own inverse

Here's another example...

y = x+1

The inverse is: x = y+1

x -1 = y

stick with lines, they are your're best bet