I am integrating (1/3)(3-x)^-1.
Is it (1/3)ln(3-x) ?
It probably isn't.
Not usually but it can be-often with logs.
It usually arises when you have the case of $\displaystyle I = ln|x| + C$
because $\displaystyle ln(a)+ln(b) = ln(ab) $ a new constant, k, is introduced such that $\displaystyle C = ln(k)$
$\displaystyle I = ln|x| + C = ln|x| + ln(k) = ln(k|x|)$ and $\displaystyle k|x| = e^I$