1. Which of the following relations defined on the integers are equivalence relations? a. aSb if and only if a|b or b|a. b. aTb if and only if if a+b is divisible by 3.

Please explain why it is or isn't an equivalence relation.

Help: Divisibility The integer x divides y if there is an integer k such that y = kx. If x divides y, we write x|y. Thus, 3| 15 because 15 = 5 x 3