What does M+2 mean????

M+2 generally refers to something that is two greater than M alone, and four greater than M-2. M on the other hand, is two LESS than M+2 and two greater than M-2. As if that weren't surprising enough, M-2 is FOUR LESS THAN M+2, and two less than M! It's kind of confusing but you'll get the hang of it eventually.