MathDB
Fuss lemma for parabolas

Source: III Caucasus Mathematical Olympiad

March 17, 2018
algebraquadratic trinomialconicsparabola

Problem Statement

Two graphs G1G_1 and G2G_2 of quadratic polynomials intersect at points AA and BB. Let OO be the vertex of G1G_1. Lines OAOA and OBOB intersect G2G_2 again at points CC and DD. Prove that CDCD is parallel to the xx-axis.