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MathNet 2022-part-04 — 197 problems (EN–VI) Question 45

Math Olympiad Vault · MathNet 2022-part-04 — 197 problems (EN–VI)

Question 45

Let $a$, $b$, and $c$ be positive real numbers such that $ab + bc + ca = 3$. Show that
$$
\frac{bc}{1 + a^{4}} + \frac{ca}{1 + b^{4}} + \frac{ab}{1 + c^{4}} \geq \frac{3}{2}
$$