1.

Show that the function `f: R_0->R_0`, defined as `f(x)=1/x`, is one-one onto,where `R_0`is the set of allnon-zero real numbers. Is the result true, if the domain `R_0`is replaced by `N`with co-domain beingsame as `R_0`?

Answer» `f: R_(**) to R_(**)`
and `" " f(x) = (1)/(x) AA x in R_(**)`
Let `x, y in R_(**) and f(x) = f(y) `
`rArr " " (1)/(x) = (1)/(y) rArr x =y`
`therefore f` is one-one.
For each `y in R_(**)`, ` " "x = (1)/(y) in R_(**)`
such that `" " f(x) = f((1)/(y)) = (1)/((1)/(y)) = y `
`therefore f `is onto.
Therefore, function `f` is one-one onto function.
Again, let `" " g: N to R_(**)`
then, `" " g(x) = (1)/(x) AA x in N`
Let `x, y in N and g(x) = g(y)`
`rArr (1)/(x) = (1)/(y) rArr x =y`
`therefore g ` is one-one.
`because ` For 12`inR_(**)` there does not exist `x in N ` such that
`g(x) = (1)/(12)`
`therefore g` is not onto.
Therefore, g is one-one but not onto.


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