# Can u gave me some examples of injective function.

1. Feb 5, 2008

### yaho8888

can u gave me some examples of injective function that is not surjective.
Is f(x)=y a injective function that is not surjective?

2. Feb 5, 2008

### sutupidmath

what about f:N--->N defined by f(n)=3n where n is from naturals, and N is the set of naturals.

1-->3
2-->6, so this function is injective since when f(n_1)=f(n_2)=>3n_1=3n_2=>n_1=n_2, but it is not surjective since there exists at least a numberf in the second N, in our case for example 1 that there are no numbers in N(the domain) such that when f(n)=1.

3. Feb 5, 2008

### sutupidmath

You can go and define such functions as much as you wish, for i just made that example up. OR are you looking for any other example in particular?

4. Feb 5, 2008

### andytoh

f:[0,1] -> R given by the identity function.

f:R -> C given by identity function.