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MathNet 2018-part-03 — 181 problems (EN–VI) Question 111

Math Olympiad Vault · MathNet 2018-part-03 — 181 problems (EN–VI)

Question 111

Show that if the real numbers $a, b, c \in [0,1]$, then
$$
\frac{3 a^{2}-2 a}{1+b^{3}+c^{3}}+\frac{3 b^{2}-2 b}{1+a^{3}+c^{3}}+\frac{3 c^{2}-2 c}{1+a^{3}+b^{3}} \leqslant 1
$$