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A Fixed Point Approach to Stability of a Quadratic Equation

M. Mirzavaziri·M. S. Moslehian
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Abstract

Using the fixed point alternative theorem we establish the orthogonal stability of quadratic functional equation of Pexider type $f(x+y)+g(x-y)=h(x)+k(y)$, where $f, g, h, k$ are mappings from a symmetric orthogonality space to a Banach space, by orthogonal additive mappings under a necessary and sufficient condition on $f$.

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M. Mirzavaziri, M. S. Moslehian. 2005-12-01. A Fixed Point Approach to Stability of a Quadratic Equation. https://doi.org/10.1007/s00574-006-0016-z

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