MathDB
18th ibmo - argentina 2003/q3

Source: Spanish Communities

April 8, 2006
inductionalgebra unsolvedalgebra

Problem Statement

Pablo copied from the blackboard the problem: Consider all the sequences of 20042004 real numbers (x0,x1,x2,,x2003)(x_0,x_1,x_2,\dots, x_{2003}) such that: x0=1,0x12x0,0x22x1,0x20032x2002x_0=1, 0\le x_1\le 2x_0,0\le x_2\le 2x_1\ldots ,0\le x_{2003}\le 2x_{2002}. From all these sequences, determine the sequence which minimizes S=S=\cdots
As Pablo was copying the expression, it was erased from the board. The only thing that he could remember was that SS was of the form S=±x1±x2±±x2002+x2003S=\pm x_1\pm x_2\pm\cdots\pm x_{2002}+x_{2003}. Show that, even when Pablo does not have the complete statement, he can determine the solution of the problem.