Say I have a relationship on integers defined by given a, b in integers, a is related to b iff a^2 = b^2

Then the equivalence class of [271] would be what?

Is it [271] = {-271} or is [271] = {271, -271}?

What I mean is, [271] is the set of all things related to 271, but would you list 271 in there as well? My guess is yes, but I just want to make sure.