In this paper, using an idea from the direct method of Hyers
and Ulam, we investigate the situations so that the generalized Hyers-Ulam
stability problem for Appolonius' equation
\begin{eqnarray}
\nonumber f(x-z)+f(y-z)={1 \over 2}f(x-y)+2f\Big(z-{x+y \over 2}\Big)
\end{eqnarray}
is satisfied.
@article{1102689125,
author = {Jun, Kil-Woung and Kim, Hark-Mahn},
title = {On the stability of Appolonius' equation},
journal = {Bull. Belg. Math. Soc. Simon Stevin},
volume = {11},
number = {1},
year = {2004},
pages = { 615-624},
language = {en},
url = {http://dml.mathdoc.fr/item/1102689125}
}
Jun, Kil-Woung; Kim, Hark-Mahn. On the stability of Appolonius' equation. Bull. Belg. Math. Soc. Simon Stevin, Tome 11 (2004) no. 1, pp. 615-624. http://gdmltest.u-ga.fr/item/1102689125/