What is the sum of the first 9 terms of the given geometric sequence?

ALgebra problem

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2 Answers

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  • 1 month ago

    3, 9, 27, 81, ...

    an = 3^n

    a9 = 19683

    sum_(n=1)^9 3^n = 29523

    Answer option:

    A. 29,523

  • 1 month ago

    3, 9, 27, 81,...1st term 3 and common ratio 3

    Sₙ = a(rⁿ - 1)/(r - 1)

    so, Sₙ = 3(3ⁿ - 1)/2

    Then, S₉ = 3(3⁹ - 1)/2 => 29,523

    Note: 3 + 9 + 27 + 81 + 243 + 729 + 2187 + 6561 + 19683 = 29523

    :)>

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