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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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