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MathNet 2024-part-02 — 168 problems (EN–VI) Question 111

Math Olympiad Vault · MathNet 2024-part-02 — 168 problems (EN–VI)

Question 111

Prove, for all positive real numbers $a$, $b$, $c$, the following inequality:
$$
\frac{a}{9 b c+1}+\frac{b}{9 c a+1}+\frac{c}{9 a b+1} \geqslant \frac{a+b+c}{1+(a+b+c)^{2}} .
$$