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Infinite series n/2^n-1

  1. Feb 10, 2009 #1
    1. The problem statement, all variables and given/known data
    so I have learned how to do different problems of series.
    but theres this problem that I spent hours last night but could not come up with anything.
    which is-


    2. Relevant equations

    I have no idea

    3. The attempt at a solution
    so from there i was able to take out 2 and end up with: 2 n /(2^n)

    i dont know how to do after that. however, i thought about doing (1/2)^n but then again it does not make sense to me.

    help needed. i will appreciate that. thanks
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 10, 2009 #2


    Staff: Mentor

    Why have you cross-posted this problem to this forum and the Precalc forum?
  4. Feb 10, 2009 #3
    Something tells me that the ratio test could helo here.
  5. Feb 10, 2009 #4


    User Avatar
    Science Advisor
    Homework Helper

    If you want to show the series converges, the ratio test can help. If you want to find the sum, the ratio test can't help. Hint: this looks like it's related to the series 1+x+x^2+x^3+.... Take a derivative. Now figure out what to put x equal to.
  6. Feb 12, 2009 #5
    i was supposed to evaluate it. I dont know how though
  7. Feb 12, 2009 #6
    i posted this problem on a different folder and i was warned because it was a wrong place to post. anyways, i think i took it off
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