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19 June, 06:27

For the geometric sequence

-1,-2,-4 ... find a8

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Answers (2)
  1. 19 June, 08:35
    0
    An=a1 (r) ^ (n-1)

    a1=first term

    r=common ratio

    so

    firs term is - 1

    each is double the prevoius

    r=2

    an=-1 (2) ^n-1

    8th term

    a8=-1 (2) ^ (8-1)

    a8=-1 (2) ^7

    a8=-1 (128)

    a8=-128

    the 8th term is - 128
  2. 19 June, 09:20
    0
    Geometric sequence formula gn = g1 (r) ^n - 1

    To find the ratio you divide g2 by g1

    G1 = first number in the series

    To find g8 you just plug 8 instead of n

    g8 = g1 (r) ^8 - 1

    g8 = - 1 (2) ^8 - 1

    g8 = - 128
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