• Korean Journal of Mathematics
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• v.20 no.1
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• pp.19-31
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• 2012

In this paper, we prove the stability in random normed spaces via fixed point method for the functional equation $$2f(x+y)+f(x-y)+f(y-x)-f(2x)-f(2y)=0$$.

• Korean Journal of Mathematics
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• v.24 no.1
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• pp.41-49
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• 2016

In this paper, using xed point method, we prove the Hyers-Ulam stability of the following functional equation $$\hspace{15}f+(x+y+z)+f({\sigma}(x)+y+z)+f(x+{\sigma}(y)+z)+f(x+y+{\sigma}(z))\\=4f(x)+4f(y)+4f(z)$$ with involution in paranormed spaces.

• Journal of the Chungcheong Mathematical Society
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• v.29 no.1
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• pp.103-108
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• 2016

In this paper, we prove the generalized Hyers-Ulam stability of the additive functional inequality $${\parallel}f(x_1+x_2)+f(x_2+x_3)+{\cdots}+f(x_n+x_1){\parallel}{\leq}{\parallel}tf(x_1+x_2+{\cdots}+x_n){\parallel}$$ in Banach spaces where a positive integer $n{\geq}3$ and a real number t such that $2{\leq}t$ < n.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.11 no.1
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• pp.85-93
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• 2007

In this paper we prove the existence of mild solutions of a first order impulsive initial value problems for functional differential equations in Banach spaces. The results are obtained by using the Lerey-Schauder nonlinear alternative fixed point theorem.

• Journal of applied mathematics & informatics
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• v.29 no.3_4
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• pp.681-696
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• 2011

In this paper, we consider the existence of mild solutions for a certain class of nonlinear impulsive functional evolution integrodifferential equation with nonlocal conditions in Banach spaces. A sufficient condition is established by using Schaefer's fixed point theorem combined with an evolution system. An example is also given to illustrate our result.

• Korean Journal of Mathematics
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• v.19 no.4
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• pp.437-451
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• 2011

In this paper, we prove the stability in random normed spaces via fixed point method for the functional equation $$f(x+2y)-2f(x+y)+2f(x-y)-f(x-2y)=0$$.

• Journal of the Korean Mathematical Society
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• v.34 no.3
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• pp.501-503
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• 1997

The existence of a unique local generalized solution for the abstract functional evolution problem of the type $$ (FDE:\phi) x'(t) + A(t, x_t)x(t) \ni G(t, x_t), t \in [0, T], x_0 = \phi $$ in a general Banach spaces is considered. It is shown that $(FDE:\phi)$ could be considered with well-known fixed point theory and recent results for the functional differential equations involving the operator A(t).

• Kyungpook Mathematical Journal
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• v.55 no.2
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• pp.313-326
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• 2015

In this paper, we present a fixed point method to prove generalized Hyers-Ulam stability of the systems of quadratic-cubic functional equations with constant coefficients in modular spaces.

• The Pure and Applied Mathematics
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• v.23 no.3
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• pp.287-307
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• 2016

Using the fixed point method, we prove the Hyers-Ulam stability of an additive-quadratic-cubic-quartic functional equation in matrix fuzzy normed spaces.

• Journal of the Chungcheong Mathematical Society
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• v.25 no.2
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• pp.201-215
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• 2012

In this paper, we prove the stability in random normed spaces via fixed point method for the functional equation $f(x+y+z+w)\;+\;2f(x)\;+\;2f(y)\;+\;2f(z)\;+\;2f(w)\;-\;f(x+y)\;-\;f(x+z)\;-\;f(x+w)\;-\;f(y+z)\;-\;f(y+w)\;-\;f(z+w)=0$.