Integrate the function $\frac{x}{\sqrt{x+4}}, x > 0$.

Let $x+4 = t$.
Then $dx = dt$ and $x = t-4$.
Substituting these into the integral:
$\int \frac{x}{\sqrt{x+4}} dx = \int \frac{t-4}{\sqrt{t}} dt$
$= \int \left( \frac{t}{\sqrt{t}} - \frac{4}{\sqrt{t}} \right) dt$
$= \int (t^{1/2} - 4t^{-1/2}) dt$
$= \frac{t^{3/2}}{3/2} - 4 \left( \frac{t^{1/2}}{1/2} \right) + C$
$= \frac{2}{3} t^{3/2} - 8 t^{1/2} + C$
$= \frac{2}{3} t^{1/2} (t - 12) + C$
Substituting back $t = x+4$:
$= \frac{2}{3} \sqrt{x+4} (x+4-12) + C$
$= \frac{2}{3} \sqrt{x+4} (x-8) + C$,where $C$ is an arbitrary constant.