试题与答案

化简再求值1x+1-x+3x2-1,其中x=-2.

题型:解答题

题目:

化简再求值
1
x+1
-
x+3
x2-1
,其中x=-2.

答案:

原式=

x-1
(x+1)(x-1)
-
x+3
(x+1)(x-1)

=

x-1-x-3
(x+1)(x-1)

=

-4
x2-1

当x=-2时,原式=-

4
3

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