MathDB
3 positive reals w product 1,sum their pairwise product sums

Source: JBMO 2008 Shortlist C2

October 14, 2017
JBMOcombinatorics

Problem Statement

Kostas and Helene have the following dialogue: Kostas: I have in my mind three positive real numbers with product 11 and sum equal to the sum of all their pairwise products. Helene: I think that I know the numbers you have in mind. They are all equal to 11. Kostas: In fact, the numbers you mentioned satisfy my conditions, but I did not think of these numbers. The numbers you mentioned have the minimal sum between all possible solutions of the problem. Can you decide if Kostas is right? (Explain your answer).