试题

题目：
3
1+a
-
6
1-a
-
12
a2-1
．
答案
解：原式=
3(a-1)
(a+1)(a-1)
+
6(a+1)
(a+1)(a-1)
-
12
(a+1)(a-1)

=
3(a-1)+6(a+1)-12
(a+1)(a-1)

=
9(a-1)
(a+1)(a-1)

=
9
a+1
．
解：原式=
3(a-1)
(a+1)(a-1)
+
6(a+1)
(a+1)(a-1)
-
12
(a+1)(a-1)

=
3(a-1)+6(a+1)-12
(a+1)(a-1)

=
9(a-1)
(a+1)(a-1)

=
9
a+1
．
考点梳理
分式的加减法．
先通分，再把分子相加减即可．
本题考查的是分式的加减法，熟知异分母分式的加减就转化为同分母分式的加减是解答此题的关键．
找相似题