问题 选择题
(1+
1
x
)÷(1-
1
x
)
等于(  )
A.
x+1
x-1
B.
x-1
x+1
C.
x2-1
x2
D.
x2
x2-1
答案

(1+

1
x
)÷(1-
1
x
)=
x+1
x
÷
x-1
x
=
x+1
x-1
,故选A.

判断题
填空题