kill(all)$

van=facebook.com/LearningCalculus$

frs(u):=fullratsimp(u)$

f(x):=frs(x^6-6*x^4-6*x^3+12*x^2-36*x+1)$ f(x);

newton(t):=float(subst(t,x,x-f(x)/diff(f(x),x)))$

newton(newton(0.02803600793431333));

newton(newton(2.856463132680504));