MathDB
JBMO 2010. Problem 1.

Source:

June 20, 2010
algebrapolynomialfunctionalgebra proposed

Problem Statement

The real numbers aa, bb, cc, dd satisfy simultaneously the equations abcd=1,   bcda=2,   cdab=3,   dabc=6.abc -d = 1, \ \ \ bcd - a = 2, \ \ \ cda- b = 3, \ \ \ dab - c = -6. Prove that a+b+c+d0a + b + c + d \not = 0.