9.3 (continue) Infinite Geometric Series
The sum of an infinite geometric series
Example: Find the sum of the infinite geometric series. For this series, a1=2 & r=0.1
Example: Find the sum of the series: So, a1=12 and r=1/3 S=18
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
Example: Write 0.181818… as a fraction. 0.181818…=18(.01)+18(.01)2+18(.01)3+… Now use the rule for the sum!
Geometric Mean The geometric mean of two numbers, a and b is