MathDB
Junior Regional Olympiad - FBH 2014 Grade 8 Problem 2

Source:

October 3, 2018
well known

Problem Statement

Find value of 11+x+xy+11+y+yz+11+z+zx\frac{1}{1+x+xy}+\frac{1}{1+y+yz}+\frac{1}{1+z+zx} if xx, yy and zz are real numbers usch that xyz=1xyz=1