Laboratory LIRST, Polydisciplinary Faculty, Departement of Mathematics, University Sultan Moulay Slimane, Beni-Mellal Morocco.
National and Capodistrian University of Athens, Section of Mathematics and Informatics, 4, Agamemnonos Str., Aghia Paraskevi, Athens 15342, Greece.
Faculty of sciences, Departement of Mathematics, University of Ibn Tofail, Kenitra, Morocco.
We show that every approximate solution of the Hosszu's functional
f(x + y + xy) = f(x) + f(y) + f(xy) for any x; y 2 R;
is an additive function and also we investigate the Hyers-Ulam stability of this
equation in the following setting
jf(x + y + xy) f(x) f(y) f(xy)j + '(x; y)
for any x; y 2 R and > 0.