Date: 10/08/98 at 14:45:55 From: Jonathan Subject: 4 square numbers make any other? Hi! In maths lesson today my maths teacher said that a mathematician discovered that you can make any number by adding together a combination of no more than 4 square numbers. He said he couldn't remember the name of the mathematician with that theory. I was wondering if you knew his name. I have just started Secondary School, and I think my teacher would be very impressed if I found out! Thank you, - Jonathan, England
Date: 10/08/98 at 15:03:04 From: Doctor Rob Subject: Re: 4 square numbers make any other? This fact is called "Bachet's Theorem." It has been claimed that this was known to Diophantus, the ancient Greek, and it was stated explicitly by Bachet in 1621, but was first proven by Joseph-Louis Lagrange in 1770. For his biography, consult this page from the MacTutor Math History Archive site at St. Andrews, and follow the link for Lagrange: http://www-history.mcs.st-and.ac.uk/history/Indexes/L.html - Doctor Rob, The Math Forum http://mathforum.org/dr.math/
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