Hey ducked.
Can you show us what you have tried? You have three properties to prove: X ~ X, X ~ Y <=> Y ~ X, and X ~ Y and Y ~ Z <=> X ~ Z. Some hints include that if a^2 = b^2 (MOD 5) then b^2 = a^2 (MOD 5) (congruence arithmetic).
thanks chiro
pretty average at this subject but i think for part a:
so if a^2 ≡ b^2 (mod 5) then b^2 ≡ a^2 (mod 5) then is it symmetric ? Also should be transitive as if a^2 ≡ b^2 (mod 5) and b^2 ≡ c^2 (mod 5) then a^2 ≡ c^2 (mod 5).
part b: can we write the set A x A so {(1,1),(1,2),(2,1),(2,2)} and then find all binary relations that are reflexive. thus not having to write out all 16 possible binary relations?
think im rambling dont really know how to put it together