83rd Kürschák Competition 1983

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1.  Show that the only rational solution to x3 + 3y3 + 9z3 - 9xyz = 0 is x = y = z = 0.
2.  The polynomial xn + a1xn-1 + ... + an-1x + 1 has non-negative coefficients and n real roots. Show that its value at 2 is at least 3n.
3.  The n+1 points P1, P2, ... , Pn, Q lie in the plane and no 3 are collinear. Given any two distinct points Pi and Pj, there is a third point Pk such that Q lies inside the triangle PiPjPk. Prove that n must be odd.

The original problems are in Hungarian. Many thanks to Péter Dombi for the translation.

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(C) John Scholes
jscholes@kalva.demon.co.uk
19 Apr 2003
Last corrected/updated 19 Apr 2003