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
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