The functon f: N->N (N is the set of Natural Number), defined byf(x)=2x+3 is:

1. Surjective
2. injective
3. not surjective
4. none of these

injective

i want whole solution

and @shiddhant bhattacharya book has given answer as (c) not surjective

and i also want to know the diff. b/w injective and not surjective