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Baltic Way 2019 · Problem 18

Number Theory

Let a,b,ca,b,c be odd positive integers such that aa is not a perfect square and

a2+a+1=3(b2+b+1)(c2+c+1).a^2+a+1=3(b^2+b+1)(c^2+c+1).

Prove that at least one of the numbers b2+b+1b^2+b+1 and c2+c+1c^2+c+1 is composite.

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Topics

Diophantine equations

Solutions

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Contest context

Results from Baltic Way 2019

11 teams

Mean score
1.1 / 5
Scores of 4 or 5
2 / 11
Estonia
0 / 5

Score distribution

08
10
21
30
40
52
All team scores
TeamScore
St. Petersburg5 / 5
Poland5 / 5
Estonia0 / 5
Lithuania0 / 5
Germany0 / 5
Norway0 / 5
Finland0 / 5
Denmark2 / 5
Sweden0 / 5
Latvia0 / 5
Iceland0 / 5