kill(all);

van=facebook.com/LearningCalculus$

f(x,y):= x^2+y^2 = a;

g(x,y):= sqrt(x^2-10*x+y^2+25)+sqrt(x^2+y^2+2*x*y + 144)=13;

g(5,0);

f(5,0);

r=sqrt(lhs(f(5,0)));