An equivalence relation is defined to be
IE given a relation, R, it is reflexive iff
IE, given a relation R, it is symmetric iff
IE, given a relation R, it is transitive iff and
Make sure these 3 properties hold. If one does not, it's not an equivalence relation.
so, say, the first one, for example.
So f is in relation with g so that if f(n) is less than or equal to g(n) for all n bigger than some natural number, say, k.
Well, is it reflexive?
It holds because f(n) = f(n) for all n, no matter what k you choose.