Answer to Question #328131 in Discrete Mathematics for Nandhini

Question

The relation R on the set A={1,2,3,4,5}is defined by the rule (a,b) €R if 3|a-b|

Answer 1

I assume, the missed condition is the following: 3 divides |a-b|.

The following pairs satisfy this condition:

$R = \{ (1, 1), (1, 4), (2, 2), (2, 5), (3, 3), (4, 4), (5, 5), (4, 1), (5, 2) \}$

which can be easily verified by the direct substitution.