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MathNet 2019-part-07 — 184 problems (EN–VI) Question 122

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

Question 122

Show that for positive numbers $x, y, z, t$ the following inequality holds:
$$
\frac{x^8+1}{x^4} + \frac{y^8+1}{y^4} + \frac{z^8+1}{z^4} + \frac{t^8+1}{t^4} \ge 2 \cdot \left( \frac{x}{y} + \frac{y}{z} + \frac{z}{t} + \frac{t}{x} \right).
$$