• Q. In a G.P., the 5th term is 512 and the 9th term is 131072 . Find the first term(a), common ratio(r) and 14th term.
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  • solve:-
    Here,
    a5 = ar4 = 512 .............. 1
    and,
    a9 = ar8 = 131072 .............. 2

    Dividing equation (2) by (1), we get.

    [ar8]/[ar4] = [131072]/[512]
    => r4 = 256
    => r4 = 44
    => r = 4


  • Equation (1) we get
    ar4 = 512
    => a44 = 512
    => a * 256 = 512
    => a = 512 / 256
    => a = 2
    ie. a = 2 and r = 4


  • Now,
    Here, first term = 2,
    common ratio = 4
    then,
    14th term is = 2*4 (14 - 1)
    = 2*4 13
    = 2*67108864
    => 14th term is = 134217728

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