A relation f from a set A to a set B is said to be a function if every element of set A has one and only one image in set B.

• In simple words, we can say that f is a relation from a non-empty set A to a non-empty set B such that the domain of f is A and no two distinct ordered pairs in f have the same first element.

If f is a function from A to B and (a, b) ∈ f,then f (a) = b, where b is called the image of a under f and a is called the...