Question

Let A={1,2} and B={3,4}. Which of the following cannot be relation from set A to set B?

(a) {(1,1), (1,2), (1,3), (1,4)}

(b) {(1,3), (1,4)}

(c) {(2,3), (2,4)}

(d) {(1,3), (1,4), (2,3), (2,4)}

The question was asked in homework.

My question is taken from Relations in portion Relations and Functions of Mathematics – Class 11

Answer 1

The correct answer is (a) {(1,1), (1,2), (1,3), (1,4)}

Explanation: A relation from set A to set B is a subset of cartesian product of A X B. In ordered pair, first element should belong to set A and second element should belongs to set B.

In {(1,1), (1,2), (1,3), (1,4)}, 1 and 2 should also be in the set B which is not so as given in question.

Hence, {(1,1), (1,2), (1,3), (1,4)} is not a relation from set A to set B.