Question

{Given A={2,3,4}, B={2,5,6,7}. Construct an example of the following.

A mapping from A to B which is not injective i.e. many-one.

Answer 1

A mapping is many ones i.e. two distinct elements have the same images.
Given $A=\{2,3,4\},B=\{2,5,6,7\}$

So, $g=\left\{\right(2,2),(3,5),(4,2\left)\right\}$ or $g=\left\{\right(2,5),(3,5),(4,2\left)\right\}$ or $g=\left\{\right(2,2),(3,5),(4,5\left)\right\}$ .....

i.e. distinct elements of A have the same images.