math

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sorry for before it is my first time using this website and this is the real question
in a geometric series t1=23,t3=92 and the sum of all of the terms of the series is 62813. How many terms are in the series?

  • math -

    t1 = 23 ---> a = 23
    t3 = 92 --->ar^2 = 92
    divide them
    r^2 = 4
    r = ± 2

    sum(n) = a(r^n - 1)/(r-1) = 62813

    If r = 2
    23( 2^n - 1)/(2-1) = 62813
    2^n - 1 = 2731
    2^n = 2732

    but ....
    n has to be a whole number, since it stands for the number of terms
    2732 is NOT a power of 2,
    so even though you typed it again with a correction , the question is still flawed.

  • math -

    Answer is 13 terms

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