math! HELP!!?

2017-07-11 11:11 pm

Given the function f(x) = 3x, find the value of f−1(81).

1) f−1(81) = 1

2) f−1(81) = 2

3) f−1(81) = 3

4) f−1(81) = 4

回答 (1)

2017-07-11 11:22 pm

✔ 最佳答案

Let
y = f (x) = 3x and g (y) = x
i.e .g is inverse of f

x = y/3
g (y) = y/3
g (x) = x/3______inverse function.
g (81) = 27

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