∫x3x+1dx
x+x22+x33-lnx+1+C
x-x22-x33-lnx+1+C
x+x22-x33-lnx+1+C
x33-x22+x-lnx+1+C
∫x3x+1dx =∫x3+1-1x+1dx =∫x3+1x+1dx+ ∫-1x+1dx =∫(x2-x+1)dx- ∫1x+1dx =x33-x22+x-lnx+1+C