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Solution of system with a parameter

Source: 2022 Israel TST 8 P1

May 21, 2022
algebraIMO 2022 tstsystem of equationsparameterization

Problem Statement

Let n>1n>1 be an integer. Find all rRr\in \mathbb{R} so that the system of equations in real variables x1,x2,,xnx_1, x_2, \dots, x_n: \begin{align*} &(r\cdot x_1-x_2)(r\cdot x_1-x_3)\dots (r\cdot x_1-x_n)=\\ =&(r\cdot x_2-x_1)(r\cdot x_2-x_3)\dots (r\cdot x_2-x_n)=\\ &\qquad \qquad \qquad \qquad \vdots \\ =&(r\cdot x_n-x_1)(r\cdot x_n-x_2)\dots (r\cdot x_n-x_{n-1}) \end{align*} has a solution where the numbers x1,x2,,xnx_1, x_2, \dots, x_n are pairwise distinct.