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290<br />

(b) Deduce that if both q and t are odd then f is irreducible.<br />

(Generalization of Question 1, IMO 1993)<br />

A219. Proposed by Mohammed Aassila, Universite Louis Pasteur,<br />

Strasbourg, France.<br />

Solve the following system:<br />

3 x + 1<br />

x<br />

= 4 y + 1<br />

y<br />

xy + yz + zx = 1 :<br />

= 5 z + 1<br />

A220. Proposed by Waldemar Pompe, student, University of<br />

Warsaw, Poland.<br />

P is an interior point of triangle ABC. D, E, F are the feet of the<br />

perpendicularsfrom P to the lines BC, CA, AB, respectively. Let Q be the<br />

interior point of triangle ABC such that<br />

\ACP = \BCQ and \BAQ = \CAP :<br />

Prove that \DEF =90 if and only if Q is the orthocentre of triangle BDF.<br />

Challenge Board Problems<br />

Editor: David Savitt, Department of Mathematics, Harvard University,<br />

1 Oxford Street, Cambridge, MA, USA 02138 <br />

C79. Proposed by Mohammed Aassila, Universite Louis Pasteur,<br />

Strasbourg, France.<br />

Let f : R + ! R + be a non-increasing function, and assume that there<br />

are two constants p>0and T >0such that<br />

Z 1<br />

for all t 2 R + .Prove that<br />

for all t T .<br />

t<br />

f (s) p+1 ds Tf(0) p f(t)<br />

f (t) f(0)<br />

T + pt<br />

T + pT<br />

C80. Suppose a1, a2, ::: ,amaretranspositions in Sn (the symmetric<br />

group on n elements) such that a1a2 am =1. Show that if the ai generate<br />

Sn, then m 2n , 2.<br />

, 1 p<br />

z<br />

;

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