MathDB
An easy ineq; ISI BS 2011, P1

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March 31, 2013
calculusinequalitiesrearrangement inequalityn-variable inequality

Problem Statement

Let x1,x2,,xnx_1, x_2, \cdots , x_n be positive reals with x1+x2++xn=1x_1+x_2+\cdots+x_n=1. Then show that i=1nxi2xin2n1\sum_{i=1}^n \frac{x_i}{2-x_i} \ge \frac{n}{2n-1}