How do you integrate $\int x(x+3)^ \left( 1/3 \right) dx$ I'm trying to do the following integral:
$\int x(x+3)^ \left( 1/3 \right) dx$
It is taken from this website. According to my source, it is to be done by substitution method. However, when I try that (using $u=x+3$), I have an $x$ term floating around, which is making things difficult. 
Could someone explain how this is done? (I'm fairly confident it can't be done by substitution). Thanks.

let $u = x+3 \Rightarrow du = 1 dx \Rightarrow \int (u-3)(u)^{\frac{1}{3}} du.$
Now distribute and solve and change back to $x$.
