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Topic: proof of an inequality
Replies: 12   Last Post: Apr 24, 2013 9:02 AM

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Paul

Posts: 401
Registered: 7/12/10
Re: proof of an inequality
Posted: Apr 23, 2013 10:24 AM
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On Tuesday, April 23, 2013 3:10:43 PM UTC+1, oercim wrote:
> Hello. I need help. Let x1,x2,...,xn be n variables and let ave(x) be aritmetic avarage of these n variables. Then, is below inequality true? How can I show if it is true?
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> x1^2+x2^2+....+xn^2>ave(x)^2
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> Thanks a lot.

For all n >=1 , you get a counterexample when x1 = x2 ... = xn = 0. This is definitely not the answer the lecturer or textbook wanted, but it shows that more care is needed in the question.

Paul Epstein



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