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MathNet 2019-part-07 — 184 problems (EN–VI) Question 44

Math Olympiad Vault · MathNet 2019-part-07 — 184 problems (EN–VI)

Question 44

Find the minimal possible value of $\frac{1}{a} + \frac{1}{b} + \frac{1}{c}$ over all positive real numbers $a, b, c$ satisfying
$$
abc = 1, \quad a+b+c = 5 \text{ and}
$$
$$
(ab+2a+2b-9)(bc+2b+2c-9)(ca+2c+2a-9) \geq 0.
$$