Evaluate the integral.

$$\int\frac{-21 e^x - 25 }{e^{2x}+6 e^x+5} dx$$
Answer: $+C$
Hint: let $u = e^x$ so that $du = e^x dx$ and thus $dx = du/u$. This substitution converts the integrand into a rational function in $u$, which can be integrated after partial fraction decomposition.