MathDB
Putnam 2017 B1

Source:

December 3, 2017
PutnamPutnam 2017

Problem Statement

Let L1L_1 and L2L_2 be distinct lines in the plane. Prove that L1L_1 and L2L_2 intersect if and only if, for every real number λ≠0\lambda\ne 0 and every point PP not on L1L_1 or L2,L_2, there exist points A1A_1 on L1L_1 and A2A_2 on L2L_2 such that PA2→=λPA1→.\overrightarrow{PA_2}=\lambda\overrightarrow{PA_1}.
Back to ProblemsView on AoPS