2001 IMO Shortlist Problems/A6
Contents
Problem
Prove that for all positive real numbers ,
![$\frac {a}{\sqrt {a^2 + 8bc}} + \frac {b}{\sqrt {b^2 + 8ca}} + \frac {c}{\sqrt {c^2 + 8ab}} \geq 1.$](http://latex.artofproblemsolving.com/b/9/9/b99abc5062d845cddcb97bb99675fe9a4de3a2ee.png)
Generalization
The leader of the Bulgarian team had come up with the following generalization to the inequality:
![$\frac {a}{\sqrt {a^2 + kbc}} + \frac {b}{\sqrt {b^2 + kca}} + \frac {c}{\sqrt {c^2 + kab}} \geq \frac{3}{\sqrt{1+k}}.$](http://latex.artofproblemsolving.com/4/7/1/471af15648323ef1d44e3ee7252c1941f2ac8f40.png)
Solution
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