The stability of d'Alembert and Jensen type functional equations

The aim of this paper is to study the stability problem of the d'Alembert type and Jensen type functional equations:f(x+y)+f(x+σy)=2g(x)f(y),f(x+y)+f(x+σy)=2g(x)f(y),f(x+y)+f(x+σy)=2f(x)g(y),f(x+y)+f(x+σy)=2f(x)g(y),f(x+y)+f(x+σy)=2f(x).f(x+y)+f(x+σy)=2f(x).