Consider the class of functional equations
g[F(x,y)] = H[g(x),g(y)],
where g: E --> X, f: E x E --> E, H: X x X --> X, E is a set and (X,d) is a complete metric space. In this paper we prove that, under suitable hypotheses on F, H and ∂(x,y), the existence of a solution of the functional inequality
d(f[F(x,y)],H[f(x),f(y)]) ≤ ∂(x,y),
implies the existence of a solution of the above equation.
@article{urn:eudml:doc:38832, title = {An existence and stability theorem for a class of functional equations.}, journal = {Stochastica}, volume = {4}, year = {1980}, pages = {23-30}, zbl = {0442.39005}, mrnumber = {MR0573723}, language = {en}, url = {http://dml.mathdoc.fr/item/urn:eudml:doc:38832} }
Forti, Gian Luigi. An existence and stability theorem for a class of functional equations.. Stochastica, Tome 4 (1980) pp. 23-30. http://gdmltest.u-ga.fr/item/urn:eudml:doc:38832/