In this paper, the invariance equation (φ1 +φ2)-1 (φ1(x) + φ2(y)) + (ψ1 + ψ2)-1(ψ1(x) + ψ-2(y)) = x + y is solved under four times continuous differentiability of the unknown functions φ1, φ2, ψ1, ψ2.
- In this paper
- the invariance equation
ASJC Scopus subject areas
- Discrete Mathematics and Combinatorics
- Applied Mathematics