‎In this paper‎, ‎we present the‎ generalized hyperstability results of cubic functional equation in‎ ‎ultrametric Banach spaces using the fixed point method‎.

In this paper, we give some properties of the bi-Jensen functional equation and investigate its Hyers–Ulam stability hyperstability. We construct a function which is not continuous. Additionally, on restricted unbounded domains. Finally, apply obtained results to study interesting asymptotic behaviors functions.

We provide three large classes of control functions that ensure the hyperstability Cauchy equation on restricted domains included in various types commutative semigroups. Among other consequences, we obtain significant improvements similar results known from literature for several Aoki-Rassias-type functions.

In this paper, we present our theoretical investigations of the technique of feedback error learning (FEL) from the viewpoint of adaptive control. We first discuss the relationship between FEL and nonlinear adaptive control with adaptive feedback linearization, and show that FEL can be interpreted as a form of nonlinear adaptive control. Second, we present a Lyapunov analysis suggesting that th...