a的平方-a-2/a的平方-4a+4减去a/a的平方-2a)除以a/a-2

解
[(a²-a-2)/(a²-4a+4)-a/(a²-2a)]÷a/(a-2)
=[(a-2)(a+1)/(a-2)²-a/a(a-2)]×(a-2)/a
=[(a+1)/(a-2)-1/(a-2)]×(a-2)/a
=(a+1-1)/(a-2)×(a-2)/a
=1