Maths Olympiad Prep

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Problem 2294

IMO Shortlist mid-range; USAMO P2/P5
Algebra Difficulty 8.4 Prove it IMO Team Selection Contest I · Estonia

Let R+\mathbb{R}^+ be the set of positive real numbers. Determine all functions f:R+R+f: \mathbb{R}^+ \to \mathbb{R}^+ satisfying the equation
xf(x2)f(f(y))+f(yf(x))=f(xy)(f(f(x2))+f(f(y2))). xf(x^2)f(f(y)) + f(yf(x)) = f(xy)(f(f(x^2)) + f(f(y^2))).
for all x,yR+x, y \in \mathbb{R}^+.

This one wants a proof. Work it on paper, then read the official solution and mark yourself. Be honest about it: the record is only any use to you if it is.

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Official solution

See IMO 2016 shortlist, problem A4. (That problem was proposed by Estonia.)

Source: MathNet, licensed CC-BY-4.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.