[(1/x -1)+(1/1-x^2)](1-1/x)=[(1-x)/x+1/(1+x)(1-x)](x-1)/x=-(x-1)^2/x^2-1/x(x+1)=[-(x-1)^2(x+1)-x(x-1)]/x^2(x+1)=-(x-1)(x^2-1+x)/x^2(x+1)
你可以来这里看看http://www.nmline.com
