kill(all)$

van=facebook.com/LearningCalculus$

f(k,x):=((k+1)*(k/16)^(1/x) - k)^x;

L:limit(f(80,x),x,inf);

Log(a,u):=log(u)/log(a)$

Log(5,L);

F:bfloat(%);

float(F);

is(equal(L, 5^81));