van=facebook.com/LearningCalculus$

f(a,b,c) := (a+b)^2+(a+b+4*c)^2 = 100*a*b*c/(a+b+c)+k;

limit(limit(limit(f(a,b,c),a,0,plus),b,0,plus),c,0,plus);

f(x,y,z);