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**hammana****Member**- Registered: 2012-03-02
- Posts: 48

If a, b, c, d are 4 positive numbers, show that

a/b+b/c+c/d+d/a>=4

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**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 14,846

Hi hammana

Have you heard of the AM-GM inequality?

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

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**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 81,747

Hi;

Have you left out some constraint on this problem?

**In mathematics, you don't understand things. You just get used to them.I have the result, but I do not yet know how to get it.All physicists, and a good many quite respectable mathematicians are contemptuous about proof.**

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