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Homework Help: Sigma Notation Problem

  1. Feb 17, 2006 #1
    Okay, I think this problem relates with sigma notation (I'm not good at it)

    the sequence given is 2, 4, 8, 16, 32 ......

    It wants you to find the sum from 1-50

    So the equation thing is 2^N?

    How do you find all the sums again...? Thanks
  2. jcsd
  3. Feb 17, 2006 #2


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    Write out the sum:

    [tex]S = 2 + 2^2 + \cdot \cdot \cdot + 2^{50}[/tex]

    If you multiply the sum by 2 you get

    [tex]2S = 2^2 + 2^3 + \cdot \cdot \cdot + 2^{50} + 2^{51}[/tex]

    What happens when you subtract the first equation from the second? Can you determine from that what the sum is?
  4. Feb 17, 2006 #3


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    If you mean something like

    [tex] S=\sum_{k=1}^{50} 2^{k} =...? [/tex]

    , i guess the notation shouldn't be too difficult to grasp.
    I hope.

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