x+1分之1 - x的平方-6x+9分之3-x * x-3分之x的平方+x等于多少？？

原式=1/(x+1)*[(x-3)/(x+3)^2+2/(x+3)]-x/(x+3)(x-3) =1/(x+1)[3(x+1)/(x+3)^2]-x/(x+3)(x-3) =3/(x+3)^2-x/(x+3)(x-3) =[3(x-3)-x(x+3)]/(x+3)^2(x-3) =-(x^2+9)/(x+3)^2(x-3)。