(1)原式=2×
-1+3 (3分)1 2
=3;(4分)
(2)原式=
÷[a?3 2(a?2)
]5?(a+2)(a?2) (a?2)
=
?a?3 2(a?2)
(6分)a?2 9?a2
=
?a?3 2(a?2)
a?2 (3+a)(3?a)
=?
. (8分)1 2(a+3)
当a=
?3时,
3
原式=?
=?1 2(
?3+3)
3
. (9分)
3
6