Question
Prove that the Greatest integer Function f : R $\rightarrow$ R, given by f(x) = [x], is neither one-one nor onto, where [x] denotes the greatest integer less than or equal to x.

Answer

Function f : R $\rightarrow$ R, given by f(x) = [x]
$\because \;1 \leqslant x \leqslant 2$, f(x) = 1
$\therefore$ f(1) = 1 and f(1.1) = 1
$\therefore$ f is not one-one.
f takes only integer values, therefore range(f) = set of integers,which is not equal to R, codomain.
Therefore, f is not onto.

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