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MathNet 2007-part-03 — 185 problems (EN–VI) Question 53

Math Olympiad Vault · MathNet 2007-part-03 — 185 problems (EN–VI)

Question 53

Show that
$$
\frac{1}{ab + 2c^2 + 2c} + \frac{1}{bc + 2a^2 + 2a} + \frac{1}{ca + 2b^2 + 2b} \geq \frac{1}{ab + bc + ca}
$$
for all positive real numbers $a$, $b$, $c$ satisfying the equality $a + b + c = 1$.