i know i am supposed to find the derivative of an equation to find [somehow] the extreme points.

but how? for example:

$\displaystyle f(x)= \frac {1}{x} + \ln(x) $

i would get this right?

$\displaystyle \frac {-1}{x^2} + \frac {1}{x}$

they give me an interval as well... $\displaystyle 0.5 \leq x \leq 4$

what do i do?