Problem A. 548. (December 2011)
A. 548. Prove that
holds for arbitrary real numbers .
Deadline expired on January 10, 2012.
Solution. Note that the factors on the left-hand side are all nonnegative.
Let S=x1+...+xn. From
Equality holds if and only if x1=...=xn-1=1.
3 students sent a solution. 5 points: Gyarmati Máté, Janzer Olivér, Omer Cerrahoglu.