Find all sets of four natural numbers such that the square of each of them, when added to the sum of the other three, again yields a perfect square.

(1,1,1,1) is a solution.

Also, (a,a,a,a), a>1 is not a solution, as a little manipulation of the resultant equation shows.

 

 

Posted by xdog on 2008-12-11 22:16:25