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MathNet 2019-part-03 — 184 problems (EN–VI) Question 32

Math Olympiad Vault · MathNet 2019-part-03 — 184 problems (EN–VI)

Question 32

If $a$, $b$, $c$ are positive real numbers, prove that:
$$
\frac{1}{ab(b+1)(c+1)} + \frac{1}{bc(c+1)(a+1)} + \frac{1}{ca(a+1)(b+1)} - \frac{3}{(1+abc)^2} \ge 0.
$$