[Potironette]

(Of course, that means the pointing end of the compass needle is in fact the compass's SOUTH pole. Don't let that confuse you.)

I thought the pointing end was the compass's north pole..?

I've explained "closed form" before. Basically it's a function that returns the same values as a sequence if you pass the natural numbers to it, but it doesn't have any recursion (that is, self-reference) in it.

Oops, I forgot ._.'''. So basically I can find the sum at any position (n) with closed form and that's what closed form is?

5c+1, because ab / ac = ab-c

So to find a ratio I just look at one value and the next and if I don't know how much to multiply the first by, I just divide the next from the previous! Although, wouldn't that be 5^c?

Without context, I have no idea on Sn = (1/2)(n(2a +(n-1)d)) = n((a1+a2)/2), because I don't know what a, a1, a2, and d are.

I messed up writing it, woops. a = a₁. And 'a' represents the first term in an arithmetic series. d is the difference between two terms in an arithmetic series. S_n in this case is the sum for the arithmetic series. I learned to use those formulas to find the sum of things such as 1, 3, 5, ... up to a specified nth term in class.