（1-x-x^2）/（x^2+x^3） =(1+x-2x-x^2)/(x^2+x^3)=1/x^2-2/x(x+1)-1/(x+1)=1/x^2 - 2*(1/x - 1/(x+1))-1/(x+1)=1/x^2 - 2/x + 1/(x+1)然后代公式就行了∫[1/x^2 - 2/x + 1/(x+1)]dx=-1/x-2lnx+ln(x+1)+C...