设y'=p,则y''=p'p'(x+1)+p(x+2)=0,当x≠-1时,两边除以x+1得p'+(x+2)/(x+1)*p=0,这是线性方程,积分得ln|p|=-x-ln|x+1|+C1即p=Ce^-x/(x+1),其中C=±e^C1
