# Integral of dx/(C-x)

• August 9th 2012, 10:35 AM
NotionCommotion
Integral of dx/(C-x)
How would I calculate the integral of

dx/(C-x)

C is a constant.

Thanks
• August 9th 2012, 10:40 AM
richard1234
Re: Integral of dx/(C-x)
A simple substitution: $u = C-x \Rightarrow du = -dx$. Therefore

$\int \frac{dx}{C-x} = -\int \frac{du}{u} = -\ln |u| + k = -\ln |C-x| + k$ (k is another arbitrary constant).
• August 9th 2012, 12:30 PM
NotionCommotion
Re: Integral of dx/(C-x)
Thanks Richard. It's coming back now. I has been a few years since I have done this!