[tex]\qquad\qquad\huge\underline{{\sf Answer}}[/tex]
The given function is :
[tex]\qquad \tt \dashrightarrow \:f(x) = \frac{1}{x} [/tex]
here, for each value of x there is an unique value of f(x), so we can infer that it's a " one - one " function.
but it isn't an onto function because for value of x as 0, we have no value of f(x) [ undefined ]