Let \(a, b, c \) be non-negative real numbers. Prove that

\[ \frac{ ab}{a+4b+4c} + \frac{bc}{b+4c+4a} + \frac{ ac}{c+4a+4b} \leq \frac{ a+b+c}{9} \]

Hi! :) I saw this difficult inequality problem on the Studying Math FB Page but haven't been able to solve it for a very long time! (No copyright intended!) Any help would be appreciated. Thanks! :)

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## Comments

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TopNewestI have some solutions :)

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Could you please give it out?I tried homogenizing, linearization.The only other ways are expanding and then using some inequality like Muirhead or Holder.

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Maybe since the inequality it homogeneous creating a condition like \(a+b+c\) might help? My other thought is try using Jensen's inequality because it's normally really useful with cyclic inequalities like this, and the \(9\) looks Jensen-esque. You could always just multiply everything up and AM-GM/ Murihead's?

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Sure! I will try it out :) Thanks!

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