Integral of $\frac{1}{100-x}$ I don't understand how the integral below:
\begin{align}
\int{\frac{1}{100-x}dx} = \ -\log|x-100| +c
\end{align}
When I integrate I get the answer:
\begin{align}
\ -\log|100-x| +c
\end{align}
I understand that it probably has something to do with the absolute value function, would someone kindly explain it to me? Thanks! 

The absolute value function disregards sign, so |4| = |-4| for example.
That also means that $|x-100| = |100-x|$. 
