Sums Of Arithmetic & Geometric Series

To find the sum of the _____ terms of an arithmetic series.

Formula: Sn= n(T1+Tn)/2

To find the sum of the _____ terms of a geometric series.

Formula: Sn= T1(1-r^n)/1-r

Series is a list of numbers that are added together.

Ex1: 2+4+6+8....

Ex2: Find the first 25 terms of the arithmetic series

11+ 14 + 17 + 20....

(This formula learned in chapter 13-1)

Tn = T1+ (n-1)d

Tn = 11+ (25-1) 3

Tn= 11+ 75 -1

Tn=83

S25= 25(11+83)/2

=1,175

1)Plug into formula learned in 13-1

2)Plug the Tn you get from that formula into the new formula.

3) Once plugged into formula and calculator, you get 1,175