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The infinite geometric series 27, -9, 3/(-1), 1/3, ... adds up to an (improper) fraction a/b in lowest terms. Find a/b.

a) a = 27, b = 28
b) a = 27, b = 29
c) a = 28, b = 27
d) a = 29, b = 27

User KoCMoHaBTa
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1 Answer

7 votes

Final answer:

After applying the sum formula for an infinite geometric series to the given series, we obtain 81/4 as the sum in lowest terms. However, this answer does not match any of the provided options, suggesting there may be an error in the question or the options given.

Step-by-step explanation:

The question asks us to find the sum of an infinite geometric series, given as 27, -9, 3/(-1), 1/3, and so on. We can use the formula for the sum of an infinite geometric series, which is S = a / (1 - r), where a is the first term and r is the common ratio. In this series, a = 27 and r = -1/3 (since each term is -1/3 of the previous term).

Substituting these values into the formula we get:

S = 27 / (1 - (-1/3)) = 27 / (1 + 1/3) = 27 / (4/3) = 27 * (3/4) = 81/4

Now, 81/4 is the sum in lowest terms, which gives us a = 81 and b = 4, but this option is not provided in the question. It seems there is a typo in the options or in the question itself. It's important to check the original series and calculations to ensure they are correct before selecting an answer.

User HGS Labs
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