Answer
$f^{-1}(x)=\log_{3}x-1$
Work Step by Step
To find the inverse of y=f(x):
1. swap x and y in the expression of the function
2. solve for y
3. replace $y $with $f^{-1}(x)$
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$y=3^{x+1}$
$ x=3^{y+1}\qquad$... apply $\log_{3}$ to both sides
$\log_{3}x=y+1\qquad$... $/-1$
$y=\log_{3}x-1$
$f^{-1}(x)=\log_{3}x-1$
