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45th Mongolian Mathematical Olympiad

Mongolia number theory

Problem

Find all integer solutions of the equation. (proposed by Ts. Dashdorj)
Solution
This equation is same as , is 17th cyclotomic polynomial. is prime number, if then or . So if for arbitrary then or . . If we have for then .

If we have then ; But polynomial is polynomial's divisor then contradict to above two cases.
Final answer
No integer solutions

Techniques

Techniques: modulo, size analysis, order analysis, inequalitiesMultiplicative orderRoots of unityPolynomial operations