International Mathematics Competition for University Students

July 31 – August 6 2017, Blagoevgrad, Bulgaria

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Day 1
    Problem 1
    Problem 2
    Problem 3
    Problem 4
    Problem 5

Day 2
    Problem 6
    Problem 7
    Problem 8
    Problem 9
    Problem 10

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    Day 1 questions
    Day 1 solutions
    Day 2 questions
    Day 2 solutions
    Closing Ceremony
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Official IMC site

Problem 7

7. Let $p(x)$ be a nonconstant polynomial with real coefficients. For every positive integer~$n$, let $$q_n(x) = (x+1)^np(x)+x^n p(x+1) .$$

Prove that there are only finitely many numbers $n$ such that all roots of $q_n(x)$ are real.

Proposed by: Alexandr Bolbot, Novosibirsk State University

Hint: Consider the sum of squares of the roots of $q_n(x)$.

  Solution