Combination of functions and their inverses.

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I was told by my teacher that that $f^{-1}(f(x))$ is equal to $x$ if $x$ belongs to the range of the inverse function. I tried verifying it for different functions and always got it right. Now, out of general curiosity, I just wanted to know what would happen if $x$ didn't belong to the range of the inverse function. In inverse trigonometric functions we use the concept of allied angles to bring $x$ in the required range but I just wanted to know about other types of functions. I tried thinking of some, but wasn't able to find one such that $x$ didn't belong to the range of the inverse function. Thanks a lot :)

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HINT Think about $f(x) = \sqrt{x}$ and $f^{-1}(x) = x^2$ with $x < 0$.