[1-1/(a-1）] -(a²-4a+4)/(a²-a)
=(a-1-1)/(a-1) - (a-2)²/[a(a-1)]
=[a(a-2)-(a-2)²]/[a(a-1)]
=[(a-a+2)(a-2)]/[a(a-1)]
=2(a-2)/[a(a-1)]
.
[a/(a-2) - a/(a+2）]· (4-a²)/a
=[a/(a-2)] · (4-a²)/a - [a/(a+2）]· (4-a²)/a
=-(a+2) - (2-a)
=-a-2-2+a
=-4