بهمن حیاتی

In this paper, we consider the stability and nonstability results for the following system of functional equations f(ax_1 + bx_2, y, z) + f(ax_1 − bx_2, y, z) = 2af(x_1, y, z), f(x, ay_1 + by_2, z) + f(x, ay_1 − by_2, z) = 2a^2f(x, y_1, z) + 2b^2f(x, y_2, z), f(x, y, az_1 + bz_2) + f(x, y, az_1 − bz_2) = ab^2(f(x, y, z_1 + z_2) + f(x, y, z_1 − z_2)) +2a(a^2 − b^2)f(x, y, z1) where a, b ∈ Z\{0}, on r-divisible abelian groups.