newbie question, 3d replotting



Is it possible to plot3d two or more functions together

e.g.
f(x,y,z) := x^z + y^z
Is it possible to combine plot3d(f(x,y,3),[x,0,5],[y,0,5]); and
plot3d(f(x,y,5),[x,0,5],[y,0,5]);

regards,
hugo