1. 9.3 (continue) Infinite Geometric Series

2. The sum of an infinite geometric series

3. Example: Find the sum of the infinite geometric series.
For this series, a1=2 & r=0.1

4. Example: Find the sum of the series:
So, a1=12 and r=1/3
S=18

5. Example: An infinite geom. Series has a1=4 & a sum of 10
Example: An infinite geom. Series has a1=4 & a sum of 10. What is the common ratio?
10(1-r)=4
1-r = 2/5
-r = -3/5

6. Example: Write 0.181818… as a fraction.
…=18(.01)+18(.01)2+18(.01)3+…
Now use the rule for the sum!

7. Geometric Mean
The geometric mean of two numbers, a and b is