If f(x) = |x|, prove that fof = f.

We have, f(x) = |x|


We assume the domain of f = R and range of f = (0,)


Range of f domain of f


fof exists,


Now,


fof(x) = f(f(x)) = f(|x|) = ||x|| = f(x)


fof = f


Hence proved.


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