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22 April, 12:48

Given the formula, Sn=a 1-r^n/1-r, what is the sum of the first nine terms of the geometric series: 324, - 108, 36, - 12 ...

If necessary, round to the hundredths place. (2 places after the decimal)

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  1. 22 April, 15:26
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    243.01.

    Step-by-step explanation:

    The first term (a) = 324.

    The common ratio (r) = - 108/324 = - 1/3.

    So sum of 9 terms is:

    S (9) = 324 * (1 - (-1/3) ^9) / (1 - (-1/3)

    = 324 (1 - (-0.00005076)) / 4/3

    = 324 * 1.00005076 / 1.33333

    = 243.012.
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