=(a-1-1)/(a-1)÷(a-2)^2/a^2
=(a-2)/(a-1)÷(a-2)^2/a^2
=a^2/(a-1)*(a-2)
=1/(-2)*(-3)
=1/6题目打错了，不要意思麻烦你从新看一看=(a-1-1)/(a-1)÷(a-2)^2/a(a-1)=(a-2)/(a-1)÷(a-2)^2/a(a-1)=a/(a-2)=-1/(-3)=1/3