What is the sum of a 7-term geometric series if the first term is 6, the last term is 24,576, and the common ratio is -4?

1 Answer
Sep 30, 2015

Answer:

#19,662#

Explanation:

There may be some nice formula for this (if so, someone please add it as a better answer).

To avoid too much thought I simply decided to evaluate the 7 terms and sum them (and because I'm feeling lazy, I let my spreadsheet to the actual calculations).
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Note that there is redundant information in this question; we didn't need to be told both that there were #7# terms and that the final term value was #24,576#