• East Asian mathematical journal
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• v.30 no.3
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• pp.271-281
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• 2014

In this paper, we consider the following cubic functional equation f(3x + y) + f(3x - y) = f(x + 2y) + 2f(x - y) + 2f(3x) - 3f(x) - 6f(y) and prove the generalized Hyers-Ulam stability for it in fuzzy normed spaces.

• Journal of the Chungcheong Mathematical Society
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• v.28 no.2
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• pp.321-330
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• 2015

In this paper, we prove the generalized Hyers-Ulam stability for the following additive-quadratic functional equation f(2x + y) + f(2x - y) = f(x + y) + f(x - y) + 4f(x) + 2f(-x) in modular spaces by using a fixed point theorem for modular spaces.

• East Asian mathematical journal
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• v.34 no.5
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• pp.693-702
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• 2018

In this paper, we consider the generalized Hyers-Ulam stability for the following additive-quadratic functional equation with involution $f(x+2y)-f(2x+y)+f(x+y)+f({\sigma}(x)+y)+f(x)-4f(y)-f({\sigma}(y))=0$ in non-Archimedean spaces.

• Journal of applied mathematics & informatics
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• v.14 no.1_2
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• pp.415-422
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• 2004

In this paper, we investigate the Hyers-Ulam stability and the super-stability of the functional equation f(x＋y＋rxy) = f(x)＋f(y)＋rxf(y)＋ryf(x) which is obtained by combining the additive Cauchy functional equation and the derivation functional equation.

• Communications of the Korean Mathematical Society
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• v.32 no.4
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• pp.915-932
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• 2017

In this paper, we introduce a new type of additive functional equations and establish the generalized Ulam-Hyers stability for it in intuitionistic fuzzy normed space by using direct and fixed point methods.

• The Pure and Applied Mathematics
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• v.18 no.3
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• pp.231-244
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• 2011

We prove the Hyers-Ulam stability for trigonometric type functional inequalities in restricted domains with time variables. As consequences of the result we obtain asymptotic behaviors of the inequalities and stability of related functional inequalities in almost everywhere sense.

• The Pure and Applied Mathematics
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• v.23 no.3
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• pp.265-285
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• 2016

In this paper, we introduce functional equations in G-normed spaces and we prove the Hyers-Ulam stability of an additive-quadratic-cubic-quartic functional equation in complete G-normed spaces by using the fixed point method.

• Journal of the Chungcheong Mathematical Society
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• v.28 no.4
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• pp.635-645
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• 2015

We will show the general solution of the functional equation $$\begin{eqnarray}f(x+ay)+f(x-ay)+2(a^2-1)f(x)\\=a^2f(x+y)+a^2f(x-y)+2a^2(a^2-1)f(y)\end{eqnarray}$$ and investigate the Hyers-Ulam stability of the quartic set-valued functional equation.

• Journal of applied mathematics & informatics
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• v.10 no.1_2
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• pp.283-295
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• 2002

In this Paper we show the Solution of the following Jensen functional equation with three variables and prove the stability of this equations in the spirit of Hyers, Ulam, Rassias and Gavruta: (equation omitted).

• Journal of the Chungcheong Mathematical Society
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• v.10 no.1
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• pp.109-116
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• 1997

In this paper, we prove a generalization of the stability by s. M. Jung[3] of the functional equation $f(x^2-y^2+rxy)=f(x^2)-f(y^2)+rf(xy)$, which can be considered as a variation of the Hosszu's functional equation.