IMO 2019 Shortlist A5
Let x1, x2, ..., xn be different real numbers. Prove that ÿ 1ďiďn ź j‰i 1 ´ xixj xi ´ xj “ 0, if n is even; 1, if n is od...
Category: Algebra
Problem
Let x1, x2, ..., xn be different real numbers. Prove that ÿ 1ďiďn ź j‰i 1 ´ xixj xi ´ xj “
0, if n is even; 1, if n is odd. (Kazakhstan) Shortlisted problems 5