kill(all);

fpprec:40;

van=facebook.com/LearningCalculus;

loG(a,x):= log(x)/log(a)$

f(x):=(x^2+4)*5^(x+6)$

g(x):=5-x$

u(x):=loG(5,4)-loG(f(x),g(x))$

u(x);

newton(t):=bfloat(subst(t,x,x-u(x)/diff(u(x),x)))$

guess:-6.635464260727666060928442026685053164984b0;

newton(guess);

bfloat(u(guess));