Let A, B be Hermitian matrices. Prove that tr(A2B2) ≥ tr((AB)2).
The best solution was submitted by Jeong, Jinmyeong (정진명), 수리과학과 2007학번. Congratulations!
Here is his Solution of Problem 2010-17.
Alternative solutions were submitted by 정성구 (수리과학과 2007학번, +3), 김치헌 (수리과학과 2006학번, +3), 박민재 (KSA-한국과학영재학교, +3).