文摘
We introduce a new functional equation (E(α)), \({\alpha \geqq 0}\) which is originating from the product in the number field \({\mathbb{Q}\left(\sqrt[4]{\alpha}\,\right)}\). We give an explicit description of the solutions \({f : \mathbb{R}^{4}\to \mathbb{R}}\) of this equation for \({\alpha \geqq 0}\) and investigate these results to find the solutions \({f : \mathbb{R}^{4} \to \mathbb{C}}\) of d’Alembert’s type and a Van Vleck’s functional equations originating from number theory. Our considerations refer to the paper [2] in which L. R. Berrone and L. Dieulefait determine, for a fixed real \({\alpha}\), the real valued solutions of the equation$$ f(x_{1},y_{1})f(x_{2},y_{2})=f(x_{1}x_{2}+\alpha y_{1}y_{2},x_{1}y_{2}+x_{2}y_{1}),\quad (x_{1},y_{1}),(x_{2},y_{2})\in \mathbb{R}^{2}.$$