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Putnam 1965 A6

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September 27, 2020
Putnam

Problem Statement

In the plane with orthogonal Cartesian coordinates xx and yy, prove that the line whose equation is ux+vy=1ux+vy = 1 will be tangent to the cirve xm+ym=1x^m+y^m=1 (where m>1m>1) if and only if un+vn=1u^n + v^n = 1 and m1+n1=1m^{-1} + n^{-1} = 1.