For n is greater than or equal to 1, use congruence theory to find remainder of:
so here's what I did - I'm new to mod(s) so I wanted to make sure it goes right:
yes??? does it work?
If what you've just read does not make sense for you (which wouldn't be surprising if you're new to "moduli"), you should avoid writing negative powers. For instance, you can notice that , hence . And you can go on like you did.
But in fact what you wrote is still right because can be understood as an inverse with respect to the multiplication modulo 7 (and not with respect to the multiplication in ). An inverse of modulo 7 is an integer such that . This happens to exist for every which is not divisible by 7, and we denote it by . The notation is the same as the notation for but the "mod 7" prevents from any confusion.
Anyway, you'll soon learn about this in more details. For now, just be conscious that dividing is not straightforward when using moduli. You can add, multiply, but not always divide. Use the trick I said about to circumvent this problem elementarily.