Let n be a positive integer. Let ω=cos(2π/n)+i sin(2π/n). Suppose that A, B are two complex square matrices such that AB=ω BA. Prove that (A+B)n=An+Bn.
The best solution was submitted by Gee Won Suh (서기원), 수리과학과 2009학번. Congratulations!
Here is his Solution of Problem 2011-15.
Alternative solutions were submitted by 박민재 (2011학번, +3, alternative solution), 장경석 (2011학번, +3).