问题
解答题
先化简,再求值:(
|
答案
(
+1)÷(1-x x+1
)•3x2 1-x2
=1 x-1
÷2x+1 x+1
•1-4x2 1-x2 1 x-1
=
•2x+1 x+1
•(1+x)(1-x) (1+2x)(1-2x)
=1 x-1
,1 2x-1
∵x=
sin45°•cot60°=3
×3
×2 2
=3 3
,2 2
∴原式
=1 2×
-12 2
=1
-12
+1.2