VN-TST 1996 Problem 3

Find the minimum value of the expression:

$f(a,b,c)= (a+b)^4+(b+c)^4+(c+a)^4 - \frac{4}{7} \cdot (a^4+b^4+c^4).$

Dataset text AI-MO AoPS. Quoted with source.

Solutions

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