先化简,再求值: ( x x+1 +1)÷(1- 3 x 2 1- x 2 )? 1 x-1 ,其中

先化简,再求值: ( x x+1 +1)÷(1- 3 x 2 1- x 2 )? 1 x-1 ,其中x= 3 sin45°?cot60°.
2025-05-20 11:21:14
推荐回答(1个)
回答1:

(
x
x+1
+1)÷(1-
3 x 2
1- x 2
)?
1
x-1
=
2x+1
x+1
÷
1-4 x 2
1- x 2
?
1
x-1

=
2x+1
x+1
?
(1+x)(1-x)
(1+2x)(1-2x)
?
1
x-1
=
1
2x-1

∵x=
3
sin45°?cot60°=
3
×
2
2
×
3
3
=
2
2

∴原式
1
2
2
-1
=
1
2
-1
=
2
+1