(3x^2+9x+7)/(x+1)-(2x^2-4x+3)/(x-1)-(x^3+x+1)/(x^2-1)不许通分,有更好的办法只是第一步不许通分啊

(3x^2+9x+7)/(x+1)-(2x^2-4x+3)/(x-1)-(x^3+x+1)/(x^2-1)=[3x(x+1)+6(x+1)+1)]/(x+1)-[2x(x-1)-2(x-1)+1])/(x-1)-[x(x^2-1)+(2x+1))/(x^2-1)=3x+6+1/(x+1) - 2x+2-1/(x-1) - x- (2x+1)/(x^2-1)=8+1/(x+1) -1/(x-1) -...