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MathNet 2019-part-01 — 184 problems (EN–VI) Question 45

Math Olympiad Vault · MathNet 2019-part-01 — 184 problems (EN–VI)

Question 45

Let $a, b, c$ be real numbers such that $0 \le a \le b \le c$. Prove that if
$$
a + b + c = ab + bc + ca \gt 0,
$$
then $\sqrt{bc}(a + 1) \ge 2$. When does the equality hold?