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A function [tex]$f[tex]$[/tex] is given by [tex]$[/tex]f(x)=3x$[/tex]. Find [tex]\left(f \circ f^{-1}\right)(3)[/tex].

A. [tex]\square[/tex] 9
B. [tex]\square[/tex] 6
C. [tex]\square[/tex] 3
D. [tex]\square[/tex] 1


Sagot :

To find \((f \bullet f^{-1})(3)\), we need to follow a few steps:

1. Determine the inverse function \(f^{-1}(x)\) of \(f(x) = 3x\):
- Given the function \(f(x) = 3x\), we want to find the inverse function \(f^{-1}(x)\).
- To find the inverse, we start with the equation \(y = 3x\), and solve for \(x\):
[tex]\[ y = 3x \implies x = \frac{y}{3} \][/tex]
- Therefore, the inverse function is \(f^{-1}(x) = \frac{x}{3}\).

2. Calculate \(f^{-1}(3)\):
- Using the inverse function \(f^{-1}(x) = \frac{x}{3}\), we substitute \(x = 3\):
[tex]\[ f^{-1}(3) = \frac{3}{3} = 1 \][/tex]

3. Calculate \(f(f^{-1}(3))\):
- We found that \(f^{-1}(3) = 1\). Now, substitute this back into the original function \(f(x) = 3x\):
[tex]\[ f(f^{-1}(3)) = f(1) = 3 \cdot 1 = 3 \][/tex]

Thus, \((f \bullet f^{-1})(3) = 3\).

The correct answer is:
C. [tex]\( \boxed{3} \)[/tex]