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MathNet 2016-part-01 — 184 problems (EN–VI) Question 32

Math Olympiad Vault · MathNet 2016-part-01 — 184 problems (EN–VI)

Question 32

Let $\alpha \in \mathbb{Q}^+$. Determine all functions $f: \mathbb{Q}^+ \to \mathbb{Q}^+$ such that
$$
f\left(\frac{x}{y} + y\right) = \frac{f(x)}{f(y)} + f(y) + \alpha x
$$
holds for all $x, y \in \mathbb{Q}^+$.
Here, $\mathbb{Q}^+$ denotes the set of positive rational numbers.