2.4.1, due on Sept 6

1) (Difficult) I had trouble understanding what a residue system was. Consequently, I struggled to also understand the lemma associated with residue systems, Lemma 2.4.1.1.

2) (Reflective) Though it was hard to understand the concept of a residue system, when they talked about a residue class, I'm fairly certain that a residue class is also referred to as an equivalence class. If they are the same, then I am most familiar with the term equivalence class ([x]).