MathDB
Inequality: (x^2 + 1)(y^2 + 1) + 4(x - 1)(y - 1) >= 0

Source: Canada Repêchage 2017/5

April 13, 2017
inequalities

Problem Statement

Prove for all real numbers x,yx, y, (x2+1)(y2+1)+4(x1)(y1)0.(x^2 + 1)(y^2 + 1) + 4(x - 1)(y - 1) \geq 0. Determine when equality holds.