Maths Olympiad Prep

Library / KöMaL problem A /3 of 136

KöMaL problem A, 2014

Algebra Difficulty 5.0 AIME, harder Prove it Hungary

Prove that
(1+a2)2x(x+y)(1+b2)2y(x+y)≥ax2by2(a+b2)2xy\left(\frac{1+a}2\right)^{2x(x+y)} \left(\frac{1+b}2\right)^{2y(x+y)} \ge a^{x^2} b^{y^2} \left(\frac{a+b}2\right)^{2xy}
holds for all real numbers a,b>0a,b>0 and xx, yy.
(5 pont)

We don't reproduce this publisher's solutions. Their own solution is here — work the problem first.
Want a route through all this instead of an archive? The track puts 2,604 problems in a working order, from Junior Challenge level to the IMO shortlist.

Source: KöMaL, licensed Rights held by KöMaL and the MATFUND Foundation. Statement reproduced verbatim; metadata (topic, difficulty) added by this project. Solutions are the publisher's, linked not copied.