SOLUTION: The second term in a geometric series is 36. The sum of the first two terms is -18. What is the first term and the common ratio? what is the sum to infinty of the series?

Algebra ->  Sequences-and-series -> SOLUTION: The second term in a geometric series is 36. The sum of the first two terms is -18. What is the first term and the common ratio? what is the sum to infinty of the series?      Log On


   

Question 673222: The second term in a geometric series is 36. The sum of the first two terms is -18. What is the first term and the common ratio? what is the sum to infinty of the series?
Answer by Edwin McCravy(20059) About Me  (Show Source):
You can put this solution on YOUR website!
The second term in a geometric series is 36. The 
sum of the first two terms is -18. What is the first 
term and the common ratio? 

what is the sum to infinity of the series?

Let the first term be x.

The sum of the first two terms is 18

So 

x + 36 = 18
     x = -18

Common ratio = %28second_term%29%2F%28first_term%29 = 36%2F%28-18%29 = -2

Therefore the sum to infinity is undefined because in order to
have a sum to infinity, the common ratio must be between -1 and 1,
exclusive of both.

Edwin