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Math Help - Sigma Notation Closed and Open Forms

  1. #1
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    Sigma Notation Closed and Open Forms

    k=1
    ending value of k=n-1
    eqn= k^3/n^2

    How do you deal with the (n-1) ending value when you are writing the sum in closed form?
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  2. #2
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    Quote Originally Posted by thinair View Post
    k=1
    ending value of k=n-1
    eqn= k^3/n^2

    How do you deal with the (n-1) ending value when you are writing the sum in closed form?
    You should know that \sum_{k=1}^n k^3 = \frac{n^2 (n+1)^2}{4}.

    Therefore \sum_{k=1}^{n-1} k^3 = \frac{(n-1)^2 n^2}{4}.
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  3. #3
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    Thank you, that is much simpler than what I was trying.
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