x2-2x+1/x2-1*x-1/x2+x-x
=(x-1)2/(x-1)(x+1) /x-1/x2+x-x
=x-1/x+1 x x2+x/x-1-x
=x(x+1)/x+1-x
=x-x
=0
因为x=0,所以无论取x值得多少,结果都是0.