>>70
x = 1+hとでもおけば
log(x)/(x-1) = log(1+h)^(1/h) → log(e) = 1

f(x)=∫[1→x]logtdt = x log(x) -(x - 1)
f(x)/(x^2 -1) = {x/(x+1)} {log(x)/(x-1)} - {1/(x+1)} → (1/2) -(1/2) = 0