Eg. :
f : A→B and f(x) = x^2
- Into function
The mapping f : A→B is called into, if there is at least one element of set B which
has no pre-image in set A.
f : A→B and f(x) = x+1
Note that 10 has no pre-image in domain A.
- Onto function
The mapping f : A→B is called onto if every element in set B has pre image in set A.
That is, a function f : A→B is called onto if its range is equal to its co-domain B.
f : A→B and f(x) = x^2
Tactile diagram may be prepared to teach this concept.
3
5
7
4
6
8
A B
10
2
4
6
4
16
36
A B
2
4
9
A B
