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Homework Help: Infinite Series

  1. Feb 23, 2009 #1
    1. The problem statement, all variables and given/known data
    I'm having trouble finding the sum of a series. I am able to perform the task for "geometric" series, where there is an "a" or an "r" value. But take the following problem for instance:
    \sum_{n=2}^\infty \frac{1}{4^n}
    I'm just not sure how to approach this problem and "prove" a solution. I know that since the numbers being added are getting smaller and smaller this sum likely converges, and I suspect it converges at (1/4). But again, how do I show this?
    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Feb 23, 2009 #2


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    Science Advisor
    Homework Helper

    That is a geometric series. It's (1/4)^n.
  4. Feb 23, 2009 #3
    Ah, indeed it is. I don't know how I missed that, I guess this post can be deleted.
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