SOLUTION: the sum of the 1st and 2nd term of a geometric progression is 10 while its sum to infinity is 18. find the fourth term
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Question 326512: the sum of the 1st and 2nd term of a geometric progression is 10 while its sum to infinity is 18. find the fourth term
Answer by galactus(183) (Show Source): You can put this solution on YOUR website!
The infinite sum is given by
The nth partial sum is given by
Since we are told the first 2 terms sum to 10, then we have
But, from the first equation,
Sub into the second equation:
and the first term, a1, is
Since the nth term is gven by ,
The fourth term is
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