If g is the inverse of f and f (2) = 4, what is f (2) + g (4) ?

The answer is 6.

When we create an inverse equation, all of the outputs become the inputs for the new equation. Therefore any time we put in a number into f (x) for x and got out y, those would be opposite in the g (x) equation. Since when we put in 2 into f (x) we get 4 out, when we put 4 into g (x), we get 2 out. Knowing this we know the following:

f (2) = 4

g (4) = 2

So when we add those two together, we get 6.