原式=-(x-2)/(x-1)÷(x²-1-3)/(x-1)
=-(x-2)/(x-1)*(x-1)/(x+2)(x-2)
=-1/(x+2)
=-1/(-3+2)
=1=-(x-2)/(x-1)*(x-1)/(x+2)(x-2)这一步不太明白÷变成乘