All russian olympiad 2016,Day 2 ,grade 9,P8 :
Let a,b,c,d be are positive numbers such that a+b+c+d=3 .Prove thata21+b21+c21+d21≤a2b2c2d21
All russian olympiad 2016,Day 2,grade 11,P7 :
Let a,b,c,d be are positive numbers such that a+b+c+d=3 .Prove that
a31+b31+c31+d31≤a3b3c3d31
Russia national 2016