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MathNet 2011 Question 51

Math Olympiad Vault · MathNet 2011

Question 51

Given an integer $n \ge 3$. Consider $n$ real numbers $x_1, x_2, \dots, x_n$ satisfying at the same time the following conditions:

i/ $x_1 \ge x_2 \ge \dots \ge x_n$;
ii/ $\sum_{i=1}^{n} x_i = 0$;
iii/ $\sum_{i=1}^{n} x_i^2 = n(n-1)$.

Find the maximum and the minimum values of the sum $S = x_1 + x_2$.