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Homework Help: Interval of Convergence

  1. Aug 3, 2012 #1


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    1. Find the radius and the interval of convergence for the series:

    Ʃ n=2 --> inf : [(-1)nxn]/ [4nln(n)]

    2.To find the radius, we use the alternating series test. **an+1/an

    3. From the alternating series test I find that the limit as n --> inf = 4. So our radius is 4. Although I do not know how to get the intervals from the radius. Can anyone help me?

    Would we just plug in ±4 for x and solve for convergence or divergence?
    Last edited by a moderator: Aug 3, 2012
  2. jcsd
  3. Aug 3, 2012 #2


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    You mean the ratio test.
    Yes. You know you have convergence for ##-4 < x < 4##. So just check to see which, if any, of the end points to include.
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