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Putnam 1975 A3

Source: Putnam 1975

February 17, 2022
Putnammaximum value

Problem Statement

Let 0<α<β<γR0<\alpha<\beta <\gamma\in \mathbb{R}. Let K={(x,y,z)R3    x,y,z0  and  xβ+yβ+zβ=1}K=\{(x,y,z)\in \mathbb{R}^{3}\;|\; x,y,z\geq 0\; \text{and}\; x^{\beta}+y^{\beta}+z^{\beta}=1\}. Define f:KR,  (x,y,z)xα+yβ+zγf:K\rightarrow \mathbb{R},\; (x,y,z)\mapsto x^{\alpha}+y^{\beta}+z^{\gamma}. At what points of KK does ff assume its minimal and maximal values?