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Classic olympiad problem · Algebra

Let P(x) be a polynomial with integer coefficients. Prove that if…

Let P(x)P(x) be a polynomial with integer coefficients. Prove that if P(a)=P(b)=P(c)=1P(a) = P(b) = P(c) = 1 for three distinct integers a,b,ca,b,c, then PP has no integer root.
Topic: Algebra Difficulty: 5/6 Expected time: ~45 min Progressive hints on Lemma: 3

This is a proof problem — the answer is an argument, not a number. The solution is deliberately not posted here: reading a solution you didn't fight for teaches almost nothing. On Lemma you attempt it cold, take one of the 3 progressive hints only when genuinely stuck, then compare your proof against a full walkthrough and mark yourself with the same rubric a competition coordinator would use.

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