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sertanlavr [38]
3 years ago
10

What is the first term in a geometric sequence if the common ratio is −2 and the sum of the first five terms is 77?

Mathematics
1 answer:
kirza4 [7]3 years ago
5 0
Answer is a1 = 7

Using equation (derived from formula to find sum of values in a geometric series),
77 \:  =  \frac{a(1 - (  { - 2}^{5}))}{1 - ( - 2)}
Hence, solve for a.
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