# Math Help - Integral of dx/(C-x)

1. ## Integral of dx/(C-x)

How would I calculate the integral of

dx/(C-x)

C is a constant.

Thanks

2. ## 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).

3. ## Re: Integral of dx/(C-x)

Thanks Richard. It's coming back now. I has been a few years since I have done this!