问题 解答题
(1)先化简,再求值:
x-2
x2-1
÷
2x+2
x2+2x+1
+
1
x-1
,其中x=
2
+1.
(2)解方程:x2-3x-1=0.
答案

(1)原式=

x-2
(x+1)(x-1)
÷
2(x+1)
(x+1)2
+
1
x-1

=

x-2
(x+1)(x-1)
(x+1)2
2(x+1)
+
1
x-1

=

x-2
2(x-1)
+
1
x-1

=

x
2(x-1)

=

x
2x-2

x=

2
+1时,

原式=

2
+ 1
2
2
+2-2
=
2
+1
2
2
=
(
2
+ 1)•
2
2
2
• 
2
=
2+
2
4

(2)∵a=1,b=-3,c=-1,

∴b2-4ac=(-3)2-4×1×(-1)=13,

∴x=

13
2×1
=
13
2

∴x1=

3+
13
2
,x2=
3-
13
2

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