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Baltic Way 2022 · Problem 4

Algebra

The positive real numbers x,y,zx,y,z satisfy xy+yz+zx=1xy+yz+zx=1. Prove that

2(x2+y2+z2)+43(1x2+1+1y2+1+1z2+1)≥5.2(x^2+y^2+z^2)+\frac43\left(\frac1{x^2+1}+\frac1{y^2+1}+\frac1{z^2+1}\right)\ge5.
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Equations and inequalities

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Contest context

Results from Baltic Way 2022

10 teams

Mean score
3.3 / 5
Scores of 4 or 5
6 / 10
Estonia
5 / 5

Score distribution

03
10
20
31
40
56
All team scores
TeamScore
Poland5 / 5
Germany3 / 5
Lithuania5 / 5
Estonia5 / 5
Denmark5 / 5
Latvia5 / 5
Sweden0 / 5
Norway0 / 5
Finland0 / 5
Iceland5 / 5