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Summing a series

  1. Jan 20, 2014 #1
    1. The problem statement, all variables and given/known data

    Find the nth term and sum to n terms of the series 12,23,60,169,494..

    2. Relevant equations



    3. The attempt at a solution
    well each term is the triple of the previous term minus some constant.
    23=10*3-7
    60=23*3-9
    ..
    ..
    This way i am able to write the nth term as 3(tn-1)-3-2n
    and hence proceed to find a telescopic sum by rearrangement and adding.
    but this method leaves me with a tn+1 which i am unable to write
    So how shud i proceed
     
  2. jcsd
  3. Jan 21, 2014 #2

    haruspex

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    I guess you meant 10,23, ...
    Please post your working as far as you got.
    Can you solve the homogeneous recurrence relation?
    To account for the extra -3-2n, just try adding a linear term with a couple of unknown constants. See if you can determine what those constants would need to be.
     
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