下列公式如何化简呢?2--------- - 2 如何化简x^2+1

2/(x^2+1)-2=2/(x^2+1)-2(x^2+1)/(x^2+1)=[2-2(x^2+1)]/(x^2+1)=[2-2x^2-2]/(x^2+1)=-2x^2/(x^2+1)