Hyperstability of bi-Cauchy-Jensen functional equations

Document Type : Research Paper


1 Department of Mathematics, Faculty of Science, Naresuan University, Phitsanulok, 65000, Thailand

2 Research Center for Academic Excellence in Mathematics, Naresuan University, Thailand


In this paper, we prove some hyperstability results of the bi-Cauchy-Jensen functional equation: $2f\left( x+y,\frac{z+w}{2} \right) = f(x,z) + f(x,w) + f(y,z) + f(y,w)$ in Banach spaces by using fixed point method.