We prove a general stability theorem of an n-dimensional quadratic-additive type functional equation [Formula: see text]by applying the direct method.

The specific force equation has many applications in open channel flow problems. Quantifying of the hydraulic jump phenomenon is an important application of this equation. This equation has a direct solution only for the rectangular channels. The trial and error procedure as well as the graphical solution are the existing methods of solving hydraulic jump equations. No direct solutions are avai...

A generalized trigonometric-quadratic functional equation of the form F(x+ y) + G(x− y) = 2H(x)K(y) + L(x) +M(y) over the domain of an abelian group and the range of the complex field is considered. Its stability is established based on the assumption that the function K is unbounded. Subject to certain natural conditions, explicit shapes of the functions H and K are determined. Several existin...