## Calculus (3rd Edition)

$\int_0^\infty \frac{dx}{e^x}$.
We compare it with $\int_0^\infty \frac{dx}{e^x}$, where $x+e^x> e^x$ and since $\int_0^\infty \frac{dx}{e^x}$ converges, then $\int_0^\infty \frac{dx}{x+e^x}$ also converges.