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Homework Help: Summation series

  1. Apr 22, 2015 #1
    1. The problem statement, all variables and given/known data

    Σ ( x^n/ln(n+5) )

    find the value of x that the above series converges
    2. Relevant equations

    3. The attempt at a solution
    i cal. it by ratio test
    and i found that |x|<1

    but when i input (-1,1) into my webwork...it said it's wrong
  2. jcsd
  3. Apr 22, 2015 #2

    Ray Vickson

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    Science Advisor
    Homework Helper

    Your answer may be overly conservative. You need to look at whether the series converges or diverges at x = +1 and at x = -1.
  4. Apr 22, 2015 #3
    Hi Cloveryeah,
    Great work, just something you've missed
    In order for the series to converge,
    Whenver n→∞ (x^n/ln(n+5)) = 0
    You said that |x| < 1, you can't try x= 1 or x = -1, it's strictly less not even equal
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