# Improper integral

1. Jul 11, 2006

### suspenc3

Hi, for some reason I cant remember and ive been looking everywhere for some info but cant find anything. Im trying to find out the answer to :

$$\int_1^i^n^f^i^n^i^t^e \frac{1}{(3x+1)^2}dx$$

what is the integral of $$\int \frac{dx}{(ax+b)^2}$$?

Thanks

2. Jul 11, 2006

### StatusX

Try the substitution u=ax+b.

3. Jul 11, 2006

### suspenc3

ahhh, got it, THanks