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    sigma notation

    \sum\limits_{k=1}^n {\left( {3k/n} \right)}

    Express the sums in closed form
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    Hello,
    Quote Originally Posted by vinson24 View Post
    \sum\limits_{k=1}^n {\left( {3k/n} \right)}

    Express the sums in closed form
    Note that the "variable" within the sum is k.

    So you can take out n and 3 :

    \sum_{k=1}^n \frac{3k}{n}=\frac 3n \sum_{k=1}^n k


    \sum_{k=1}^n k=\frac{n(n+1)}{2} (it's a known sum)


    Hence \sum_{k=1}^n \frac{3k}{n}=\frac 3n \times \frac{n(n+1)}{2}=\frac{3(n+1)}{2}
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    thanks thats alot easier than the book shows it
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