1. 6.8B– Sum of a Geometric Series
Objective: TSW find the sum of a geometric series.

2. Definitions…
Geometric series – the sum of the terms of a geometric sequence. To find the sum of the series…two possible formulas:
Given
The sum Sn of the first n terms is:
a1 and n
Sn =
a1 and an

3. Examples: Find the sum of each geometric series.
1. a1 = 16, r = 2 and n =8

4. 2. a1 = -27, r = -1/3 and n = 6

5. Examples: find the indicated term described.
3. Sn = 300, an = 160, and r = 2; a1

6. Find the indicated term then the first 3 terms.
4. Sn = 1020, an = 4, and r = 1/2; a1

7. Homework…
Pgs #’s 42-45(all), 51-56(all), 86-89(all)