分式值为0,分子=0,分母≠0
(x²-1)/(x²-x)=(x+1)(x-1)/[x(x-1)]
分式有意义,分母≠0,x≠0且x≠1
分子=0
(x+1)(x-1)=0
x=-1或x=1(舍去)
x=-1