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A difficult Series problem!

  1. Apr 10, 2012 #1
    1. The problem statement, all variables and given/known data
    Show that the series Ʃ 1 to ∞ ((-1)^n)*(n+1)/5^n converges using the alternating series test.


    2. Relevant equations



    3. The attempt at a solution
    I don't know how to show the series is decreasing. I took the derivative of the function, but it got messy and I don't feel that was the correct way to go. Any help appreciated, thanks.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Apr 10, 2012 #2

    LCKurtz

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    Have you played with the inequality you get when you write ##a_{n+1}\le a_n##? Show us what you get...
     
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