化簡:(1−1a−1)÷a2−4a+4a2−a.

化簡:(1−1a−1)÷a2−4a+4a2−a.

原式=a−1−1a−1×a(a−1)(a−2)2=a−2a−1×a(a−1)(a−2)2=aa−2.