Suppose that \(f\) is a function and \(f^{-1}\) is the inverse of \(f\). If \(f(1)=2\), \(f(2) = 6\), and \(f(3)=5\), then what is \(f^{-1}(f^{-1}(6))\)?
f(1) = 2 ⇒ f-1(2) = 1
f(2) = 6 ⇒ f-1(6) = 2
So
f-1 (f-1 (6) ) = f-1 (2) = 1