9;

kill(all)$

van=facebook.com/LearningCalculus$

f(x,y):= (x^3-y^3)/((x-y)^3 + 3*x*y);

van=facebook.com/LearningCalculus$

g(x,y):= (x^3-y^3)/((x-y)^2 + 3*x*y);

van=facebook.com/LearningCalculus$

h(x,y):= (x^3-y^3)/((x-y)^9 + 3*x*y);