(x^3-3x^2+4x-9)/(x^2+3)=x-3+x/(x^2+3)
原式=∫xdx-∫3dx+∫x/(x^2+3) dx
=x^2/2-3x+1/2∫d(x^2+3)/(x^2+3)
=x^2/2-3x+ln(x^2+3)/2+C