$\ln|x|$ vs.$\ln(x)$? When is the $\ln$ antiderivative marked as an absolute value? One of the answers to the problems I'm doing had straight lines:
    $$ \ln|y^2-25|$$
versus another problem's just now:
    $$ \ln(1+e^r) $$
I know this is probably to do with the absolute value.  Is the absolute value marking necessary because #1 was the antiderivative of a squared variable expression that could be either positive or negative (and had to be positive because, well, natural log) and the second was positive by default?
Sorry if this is me asking and answering my own question; I'd just love to get confirmation in case I'm wrong.

logarithm is a function only defined on domain $(0,\infty)$, so it make no sense to input negative value.
