Hey folks, Do anyone of you still remember the problems related to equivalence relations? Can anyone tell me if the following relations are equivalence relations on the set of integers(z)? 1. "x is related to y" if n only if x=-y 2."x is related to y" if n only if x=3y 3. "x is related to y" if n only if x divides y. 4. "x is related to y" if n only if xy>=0 5. "x is related to y" if n only if x-y is a multiple of 6. My guess is that 1,2,3,5 are equivalence relations but I remember nothing about it now... Any inputs welcome...