Suppose f(x) is an invertible function, and suppose that f(2)=f^{-1}(2)=4. What is the value of f(f(2))?
We know that f (2) = 4
So f(f(2)) = f(4)
If f-1(2) = 4 then f(4) = 2
So
f(f(2)) = f(4) = 2
