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Algebra with tangents to quadratics

Source: 2024 All-Russian Olympiad Regional Round

February 23, 2024
quadraticsderivativetangentconicsparabolaalgebra

Problem Statement

Graph G1G_1 of a quadratic trinomial y=px2+qx+ry = px^2 + qx + r with real coefficients intersects the graph G2G_2 of a quadratic trinomial y=x2y = x^2 in points AA, BB. The intersection of tangents to G2G_2 in points AA, BB is point CC. If CG1C \in G_1, find all possible values of pp.