问题 解答题
(1)计算:
1
12
-
(1-
3
)
2
+(2-
5
)0+(-
1
2
)-1

(2)先化简,再求值:
x2-2x
x2-1
÷(x-1-
2x-1
x+1
)
,其中x=
2
+1
答案

(1)

1
12
-
(1-
3
)
2
+(2-
5
0+(-
1
2
-1

=

3
6
-(
3
-1)+1-2

=

3
6
-
3
+1+1-2

=-

5
3
6

(2)

x2-2x
x2-1
÷(x-1-
2x-1
x+1

=

x(x-2)
(x+1)(x-1)
÷
x2-1-2x+1
x+1

=

x(x-2)
(x+1)(x-1)
×
x+1
x(x-2)

=

1
x-1

当x=

2
+1时,原式=
1
x-1
=
1
2
+1-1
=
2
2

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