Given the function f(x) = 3x, find the value of f−1(27).

Question

f−1(27) = 1 f−1(27) = 3 f−1(27) = 9 f−1(27) = 81

Answer 1

f(x)=27 when x=9.  The point is then (9, 27).  If we switch places with x and y, we get (27, 9).

 

f^-1(27) = 9

Answer 2

the inverse function of f(x) is f^-1(x) = (1/3)(x).  Now you can find the answer, by substituting 27 into the formula for inverse.