Answer
$$ f^{-1}(x)=\sqrt{x-1}$$
Work Step by Step
Given:
$ y=x^{2}+1$
We solve for $x$:
$\Rightarrow x^{2}=y-1$
$\Rightarrow x=\sqrt{y-1}$
Interchanging $ x $ and $ y $, we get:
$y=\sqrt{x-1}=f^{-1}(x)$
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