(a) Determine if the geometric series converges or diverges, and (b) if it converges, find its sum.
What is a?
(a) The ratio is r = 0.8. Since |r| < 1, this series converges.
(b) Since the sum starts at n = 5, the first term of the series is
a = 4(0.8)5 = 1.31072.
The sum of the series is