Q. 9 A5.0( 6 Votes )

Let be a binary operation on the set Q of rational numbers as follows:

a b = a – b

Find which of the binary operations are commutative and which are associative.

Answer :

It is given that be a binary operation on the set Q of rational numbers as

a b = a – b


We can observed that for 2,3,4 ϵ Q


2 * 3 = 2-3 = -1 and 3 * 2 = 3-2 =1


2 * 3 ≠ 3 * 2


the operation * is not commutative.


Also, (2 * 3) * 4 = (-1) * 4 = -1 -4 = -5 and


2 * (3 * 4) = 2 * (-1) = 2 – (-1) = 3.


(2 * 3) * 4 ≠ 2 * (3 * 4)


Therefore, the operation * is not associative.


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