In this paper we consider a functional inequality of the form f(x(1) x(2), y(1) + y(2)) less than or equal to f(x(1), y(1)) + f(x(2), y(2)
), for each (x(i), y(i)) is an element of C, i = 1, 2, where f: C -->
R and C is some cone in R(2). If the function f satisfies some conditi
ons we obtain the general solution. (C) 1996 Academic Press, Inc.