I.3.1.67 Indefinite Integrals

Condition: integrate rational functions. 1) \ (\ int \ frac {d x} {x^{3} +3 x^{2} +2 x} \); 2) \ (\ int \ frac {d x} {x^{3}+x} \) 3) \ \ (\ int \ frac {(x+3) d x} {x (x+1) (x+2)} \).