SOLUTION: The first 2 terms of a geometric series have a sum of -4. The fourth and fifth terms have a sum of 256. Find the first term and the common ratio of the series.

Question 726593: The first 2 terms of a geometric series have a sum of -4. The fourth and fifth terms have a sum of 256. Find the first term and the common ratio of the series.
Answer by KMST(5328) (Show Source): You can put this solution on YOUR website!
In a geometric series each term equals the previous one times the common ratio:
(recursive formula)
so that all terms can be calculated as a function of the first term as

In this problem,

and we want to find and

MY WAY:

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ANOTHER WAY:

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