I don't get the step in the red box.

But.. here's what I have:

$\displaystyle

I = e^{ \int \frac{x}{x^2 + 5} \, dx}$

$\displaystyle I = e^{\int x \frac{1}{x^2 + 5} \, dx}$

$\displaystyle I = e^{\frac{1}{2}x^2 + ln(x^2 + 5)}$

$\displaystyle I = e^{\frac{1}{2}x^2}e^{ln(x^2 + 5)}$

$\displaystyle I = e^{x}(x^2 + 5)$