$I=\int \frac{x+1}{x^{2}+5 x+6} d x$
Let $\quad \frac{x+1}{(x+3)(x+2)}=\int\left[\frac{x+1}{(x+3)(x+2)}\right] d x$
$\therefore x+1=A(x+2)+B(x+3)$
When $x=-2$, we get $B=-1$
When $x=-3$, we get $A=2$
$\therefore I=\int\left[\frac{2}{x+3}-\frac{B}{x+2}\right] d x$
$\therefore 2 \log |(x+3)|-\log |x+2|+c$