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MathNet 2023-part-05 — 191 problems (EN–VI) Question 35

Math Olympiad Vault · MathNet 2023-part-05 — 191 problems (EN–VI)

Question 35

A triple of integers $(a, b, c)$ is called *artistic* if the number $\frac{ab+bc+ca}{a+b+c}$ is also an integer.

a) Determine the integers $n$ for which the triples $(n, n+1, n+3)$ are artistic.

b) If $(x, y, z)$ is an artistic triplet, prove that $\frac{x^4+y^4+z^4}{x+y+z}$ is an integer.