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An arithmetic & geometric progression question.

  1. Apr 1, 2005 #1
    I have an arithmetic series, with the sum of the first n terms to be 610. The 1st, 3rd and 11th terms of this AP is the same as the 3rd, 2nd and 1st term of a geometric series. Find the first term of the geometric series.

    I have constructed 4 equations from this

    [tex] a_p = a_q r^2 [/tex]

    [tex]a_p+2d = a_q r [/tex]

    [tex] a_p + 10d =a_q [/tex]

    [tex] 20a_p +19d =610 [/tex]

    where p represents the AP and Q represents the GP.

    But i seem to have problems solving them simultaneously. Can anyone provide some insight?
  2. jcsd
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