Document Type : Research Paper


1 Department of Mathematics, Sirjan University of Technology, P.O.Box 7813733385, Sirjan, Iran.

2 Teacher of Mathematics, Fars education, Shiraz, Iran.


In this paper, we introduce and solve a system of bi-Drygas functional equations 
        &f(x,y+z)+f(x, y-z)=2f(x,y)+f(x,z)+f(-x,-z)\nonumber
for all $x,y,z\in X$. We will also investigate the Hyers-Ulam stability of the system of bi-Drygas functional equations.


Main Subjects

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