1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Find an expression for the sum of the series

  1. Feb 29, 2012 #1
    1. The problem statement, all variables and given/known data

    (1x2x6) + (2x3x7) + ... + n(n + 1)(n + 5)



    2. Relevant equations

    Find an expression for the sum of the series. Give your answer as a product of linear factors in n.


    3. The attempt at a solution

    I haven't tried it since I don't know what to do.
     
  2. jcsd
  3. Feb 29, 2012 #2

    Delphi51

    User Avatar
    Homework Helper

    I haven't seen one of those for years! They are interesting. There is some theory saying that the sum is equal to a polynomial with one degree higher than the term. Your terms are 3rd degree, so you need a 4th degree polynomial:
    S = a*n^4 + b*n^3 + c*n^2 + d*n + e
    By hand you figure out the sum and the powers for n = 1, 2, 3, 4, and 5.
    That gives you a system of 5 equations with 5 unknowns a, b, c, d, e.
    Solve the system to get the unknown coefficients.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Find an expression for the sum of the series
  1. Sum of series (Replies: 12)

  2. Sum of a series. (Replies: 16)

  3. Sum of series (Replies: 3)

Loading...