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n points in space, 3d combo geo - All-Russian MO 1999 Regional (R4) 10.3

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September 25, 2024
geometrycombinatoricscombinatorial geometry

Problem Statement

There are nn points in general position in space (no three lie on the same straight line, no four lie in the same plane). A plane is drawn through every three of them. Prove that If you take any whatever n3n-3 points in space, there is a plane from those drawn that does not contain any of these n3n - 3 points.