# Math Help - Integration Question

1. ## Integration Question

Hi,

I'd like to know how to go about solving the following types of questions:

Find $\int_{0}^{3}f(3x)dx$ if $\int_{0}^{9}f(x)dx=5$

2. Originally Posted by Stroodle
Hi,

I'd like to know how to go about solving the following types of questions:

Find $\int_{0}^{3}f(3x)dx$ if $\int_{0}^{9}f(x)dx=5$

Make the u sub $u=3x \implies du=3dx$ and note that when
$x=0 \iff u=0 \text{ and } x=3 \iff u=9$ are your new limits of integration.