Question

Given A = {2, 3, 4}, B = {2, 5, 6, 7}.
Construct an example of each of the following
(i) an injective mapping from A to B.
(ii) a mapping from A to B which is not injective.
(iii) a mapping from B to A.

Answer 1

(i) An injective (i.e. one-one) mapping A to B may be defined as
$f=(2,5),(3,7),(4,6)$
(ii) A mapping from A to B which is not injective may be defined as
$g=(2,2),(3,5),(4,2)$. It is many-one.
(iii) A mapping from B to A may be defined as
$h=(2,2),(5,3),(6,4),(7,4)$.