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! 

Since the argument of the logarithm is in absolute value signs, it doesn't really matter the order in a case like this. As we can see,
$$|a-b| = |(-1)(b-a)| = |-1||b-a| = |b-a|$$
