Consider the function $\displaystyle f(x) = \frac{\ln(x)}{x^{3}}$. For this function there are two important numbers $A<B$ which are either critical or outside the domain of $f(x)$:
$A =$
$B =$
For each of the following intervals, tell whether $f'(x)$ is positive (type in $+$) or negative (type in $-$).
$(A, B)$:
$(B,\infty)$:
Thus we conclude that $f(x)$ has a local at $B$ (type in MAX or MIN).