I won't give you the complete answer. Did you check reflexivity of R? Where did you get stuck?

More generally, let A and B be sets and let be a function. If R is a binary relation on A defined by iff , then R is an equivalence relation. Your question is a special case of this.

A couple of remarks about English from a non-native speaker.

1. "May I have a question about equivalence class?" Of course you may. Nobody can forbid you tohavequestions. Sometimes you are not allowed toaskquestions, though. But this forum exists so that people can ask questions, so there is no need to ask permission.

2. "With all due respect, could you give me a hint for the questions?" Usually, "With all due respect" is followed by some phrase that may appear to challenge that respect. For example, "With all due respect, I refuse to follow this unconstitutional order!"