Korean J. Math. Vol. 19 No. 2 (2011) pp.149-161
DOI: https://doi.org/10.11568/kjm.2011.19.2.149

STABILITY OF THE JENSEN TYPE FUNCTIONAL EQUATION IN BANACH ALGEBRAS: A FIXED POINT APPROACH

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Choonkil Park
Won-Gil Park
Jung Rye Lee
Themistocles M. Rassias

Abstract

Using fixed point methods, we prove the generalized Hyers-Ulam stability of homomorphisms in Banach algebras and of derivations on Banach algebras for the following Jensen type functional equation:

$$ f ( \frac{x+y}{2} ) + f ( \frac{x-y}{2} ) = f(x) $$



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