Difference between revisions of "1976 IMO Problems/Problem 5"

(See also)
Line 1: Line 1:
 
== Problem ==
 
== Problem ==
{{problem}}
+
We consider the following system
 +
with <math>q = 2p</math>:
 +
 
 +
<math>\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} + \ldots + a_{pq}x_{q} = 0, \\
 +
\end{matrix}</math>
 +
 
 +
in which every coefficient is an element from the set <math>\{ - 1,0,1\}</math><math>.</math> Prove that there exists a solution <math>x_{1}, \ldots,x_{q}</math> for the system with the properties:
 +
 
 +
'''a.)''' all <math>x_{j}, j = 1,\ldots,q</math> are integers<math>;</math>
 +
 
 +
'''b.)''' there exists at least one j for which <math>x_{j} \neq 0;</math>
 +
 
 +
'''c.)''' <math>|x_{j}| \leq q</math> for any <math>j = 1, \ldots ,q.</math>
  
 
== Solution ==
 
== Solution ==

Revision as of 09:45, 26 February 2008

Problem

We consider the following system with $q = 2p$:

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

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

This problem needs a solution. If you have a solution for it, please help us out by adding it.

See also

1976 IMO (Problems) • Resources
Preceded by
Problem 4
1 2 3 4 5 6 Followed by
Problem 6
All IMO Problems and Solutions