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1976 IMO Problems/Problem 5

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Problem

We consider the following system with q = 2p:

\begin{matrix} a_{11}x_{1} + \ldots + a_{1q}x_{q} = 0, \\a_{21}x_{1} + \ldots + a_{2q}x_{q} = 0, \\\ldots , \\a_{p1}x_{1} + \...

in which every coefficient is an element from the set \{ - 1,0,1\}. Prove that there exists a solution x_{1}, \ldots,x_{q} for the system with the properties:

a.) all x_{j}, j = 1,\ldots,q are integers;

b.) there exists at least one j for which x_{j} \neq 0;

c.) |x_{j}| \leq q for any j = 1, \ldots ,q.

Solution

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See also

1976 IMO (Problems)
Preceded by
Problem 4
1 2 3 4 5 6 Followed by
Problem 6
Want to learn how to tackle those tough AMC/AIME/Olympiad counting and probability problems? Check out Art of Problem Solving's Intermediate Counting & Probability by David Patrick.
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