化简分式x2−1x2+2x+1−x+1/x−1,并从-2,-1,0,1,2中选一个能使分式有意义的数代入求值.

问题描述:

化简分式

x2−1
x2+2x+1
x+1
x−1
,并从-2,-1,0,1,2中选一个能使分式有意义的数代入求值.

原式=

(x−1)(x+1)
(x+1)2
x+1
x−1

=
x−1
x+1
x+1
x−1

=
(x−1)2(x+1)2
(x−1)(x+1)

=
−4x
x2−1

把x=0代入,得:原式=0;
或把x=2代入,得:原式=
−4×2
22−1
=−
8
3

或把x=-2代入,得:原式=
−4×(−2)
(−2)2−1
8
3