does it look easy?
Source: Iran(third round)2003
March 8, 2004
Gaussnumber theoryrelatively primenumber theory unsolved
Problem Statement
suppose this equation: x 2 +y 2 +z 2 =w 2 . show that the solution of this equation ( if w,z have same parity) are in this form:
x=2d(XZ-YW), y=2d(XW+YZ),z=d(X 2 +Y 2 -Z 2 -W 2 ),w=d(X 2 +Y 2 +Z 2 +W 2 )