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Math Help - Proof of a summation=0?

  1. #1
    asq
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    Proof of a summation=0?

    Prove that sum that :

    Sum ( i=1 to N) of ( Xi-Xbar)/ N ((X^2)bar - (Xbar)^2) = 0

    I know this is something simple like putting everything in terms of Xi/N and cancelling but my brain isn't working today...please help?
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  2. #2
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    Quote Originally Posted by asq View Post
    Prove that sum that : Sum ( i=1 to N) of ( Xi-Xbar)/ N ((X^2)bar - (Xbar)^2) = 0
    I have a hard time reading the post But this may help.
    \;\overline X  = \dfrac{{\sum\limits_{n = 1}^N {x_n } }}<br />
{N}\, \Rightarrow \,\,\sum\limits_{n = 1}^N {\overline X }  = N\overline X  = \sum\limits_{n = 1}^N {x_n }
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  3. #3
    asq
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    Yeah, as I said my brain just didn't want to work. I realized that the denominator in that fraction can be factored out (not dependent on i) and then its just very simple to proof that sum Xn-xbar=0.

    Thanks!
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