Commun. Korean Math. Soc. 2016; 31(1): 131-138
Printed January 31, 2016
https://doi.org/10.4134/CKMS.2016.31.1.131
Copyright © The Korean Mathematical Society.
Jaeyoung Chung and Prasanna K. Sahoo
Kunsan National University, University of Louisville
We determine the general solutions $f:\mathbb R^2 \to \mathbb R$ of the functional equation $ f(ux-vy, uy+v(x+y))=f(x, y)f(u, v) $ for all $x, y, u, v\in \mathbb R$. We also investigate both bounded and unbounded solutions of the functional inequality $ |f(ux-vy, uy+v(x+y))-f(x, y)f(u, v)|\le \phi(u, v) $ for all $x, y, u, v\in \mathbb R$, where $\phi:\mathbb R^2 \to \mathbb R_+$ is a given function.
Keywords: exponential type functional equation, general solution, multiplicative function, Proth identity, stability, bounded solution
MSC numbers: 39B82
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