MathDB
Putnam 2009 A1

Source:

December 7, 2009
Putnamfunctionlinear algebramatrixgeometry3D geometrygeometric transformation

Problem Statement

Let f f be a real-valued function on the plane such that for every square ABCD ABCD in the plane, f(A)\plus{}f(B)\plus{}f(C)\plus{}f(D)\equal{}0. Does it follow that f(P)\equal{}0 for all points P P in the plane?