问题
解答题
先化简,再求值:
|
答案
-2 x+1
÷1 x2-1 x x2-2x+1
=
-2 x+1
×1 (x+1)(x-1) (x-1)2 x
=
-2 x+1
(3分)x-1 x(x+1)
=
-2x x(x+1) x-1 x(x+1)
=2x-x+1 x(x+1)
=x+1 x(x+1)
=
,(4分)1 x
当x=5时,原式=
=1 x
.(5分)1 5
先化简,再求值:
|
-2 x+1
÷1 x2-1 x x2-2x+1
=
-2 x+1
×1 (x+1)(x-1) (x-1)2 x
=
-2 x+1
(3分)x-1 x(x+1)
=
-2x x(x+1) x-1 x(x+1)
=2x-x+1 x(x+1)
=x+1 x(x+1)
=
,(4分)1 x
当x=5时,原式=
=1 x
.(5分)1 5