olymmath

BxMO 2010

Benelux Mathematical Olympiad 2010.

Other problems

Problem 1

A finite set of integers is called bad if its elements add up to 2010. A finite set of integers is a Benelux-set if none of its subsets is bad. Determine the smallest integer nn such that the set {502,503,504,…,2009}\{502,503,504, \ldots, 2009\} can be partitioned into nn Benelux-sets. (A partition of a set SS into nn subsets is a collection of nn pairwise disjoint subsets of SS, the union of which equals SS.)

Problem 2

Find all polynomials p(x)p(x) with real coefficients such that

p(a+b−2c)+p(b+c−2a)+p(c+a−2b)=3p(a−b)+3p(b−c)+3p(c−a)p(a+b-2 c)+p(b+c-2 a)+p(c+a-2 b)=3 p(a-b)+3 p(b-c)+3 p(c-a)

for all a,b,c∈Ra, b, c \in \mathbb{R}.

Problem 3

On a line ll there are three different points A,BA, B and PP in that order. Let aa be the line through AA perpendicular to ll, and let bb be the line through BB perpendicular to ll. A line through PP, not coinciding with ll, intersects aa in QQ and bb in RR. The line through AA perpendicular to BQB Q intersects BQB Q in LL and BRB R in TT. The line through BB perpendicular to ARA R intersects ARA R in KK and AQA Q in SS. (a) Prove that P,T,SP, T, S are collinear. (b) Prove that P,K,LP, K, L are collinear.

Problem 4

Find all quadruples (a,b,p,n)(a, b, p, n) of positive integers, such that pp is a prime and

a3+b3=pna^{3}+b^{3}=p^{n}