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TST

Vietnam algebra

Problem

Let , and be non-negative real numbers such that Prove that .
Solution
Let , and , we have

We need to prove that or . Since , the inequality is equivalent to: Notice that implies . We distinguish two cases regarding the value of .

If then , so the first inequality is true.

If then , so we have to prove that On the other hand, implies , so inequality (2) is true. Therefore, the inequality (1) is true.

Techniques

Symmetric functionsCauchy-SchwarzQM-AM-GM-HM / Power Mean