CHO A, B, C > 0. CHỨNG MINH ( A 2 + B 2 + C 2 )    A B B C C...

18) Cho a, b, c > 0. Chứng minh ( ^{a 2 + b 2 + c 2} ) ^{ } _ a b b c c a ¹ ₊ ^{+ 1} ₊ ⁺ ₊ ^{1  ÷} _ ^{≥ 3} ₂ ^{( a b c + + )}

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