计算:(a+2/a2−2a−a−1a2−4a+4)÷4−aa2−2a.

问题描述:

计算:(

a+2
a2−2a
a−1
a2−4a+4
4−a
a2−2a

原式=[

a+2
a(a−2)
-
a−1
(a−2)2
4−a
a(a−2)

=[
a+2
a(a−2)
-
a−1
(a−2)2
]•
a(a−2)
4−a

=
a+2
4−a
-
a(a−1)
a−2
×
1
4−a

=
(a+2)(a−2)−a(a−1)
(4−a)(a−2)

=
a−4
(4−a)(a−2)

=-
a−4
(a−4)(a−2)

=-
1
a−2