For one to one function each element in the domain is mapped on to an one and only one element in the co-domain.
The could be some elements in the co-domain that are not being used.
For a function to be one to one, then for
[tex]f(x) = f(y) [/tex]
if and only if
[tex]x = y[/tex]
For an onto function all the elements in the co-domain must be used up.
In order words, the [tex] <B>co-domain=Range</B>[/tex]
The condition is
[tex]f(x) \rightarrow \: y[/tex]
Meaning each [tex] <B>OBJECT</B>should have an <B>IMAGE</B>[/tex]
