### Abstract

In this paper the functional equation F(x + G(t(H(y-x))) = S(A(t)K(x), B(t)K(y)), x,y ε I, x ≤ y, t ε [0,1], is solved under monotonicity and injectivity assumptions for the unkown functions involved. This equation turned out to be useful in the axiomatic treatment of various joint-receipt utility structures. After several reduction steps, the solution of the above equation is reduced to that of Δ^{-1}(Δ(h(u)/H(u + v)) · H(x)/H(x+u+v)) - H(u)H(x+u+v)/H(u+v)H(x+u), x,u,v > 0, X+u+v ε I. Assuming that H and Δ are strictly monotonic, it is shown that H is a log-concave function, and as a consequence, using Lebesgue's theorem, the everywhere-differentiability of F is deduced. Then, differentiating this equation, a functional differential equation for H is derived. The solutions of this new equation are then determined and the form of Δ is described. Thus, the general solution of the original equation is also obtained.

Original language | English |
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Pages (from-to) | 273-286 |

Number of pages | 14 |

Journal | Aequationes Mathematicae |

Volume | 59 |

Issue number | 3 |

DOIs | |

Publication status | Published - Jan 1 2000 |

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### Keywords

- Choice models
- Composite functional equations
- Utility models

### ASJC Scopus subject areas

- Mathematics(all)
- Discrete Mathematics and Combinatorics
- Applied Mathematics

### Cite this

*Aequationes Mathematicae*,

*59*(3), 273-286. https://doi.org/10.1007/s000100050127