11.(2008山东威海)先化简，再求值：，其中．

解：　 　………………………………………2分

＝　　　　 …………………………………………………………3分

＝　　　　 …………………………………………………………4分

＝．　　　　 ……………………………………………………………………5分

当时，原式＝．　 ……………………………………7分

10. (2008浙江宁波)化简．

解：原式···················································································· 2分

························································································· 4分

9.(2008年四川省宜宾市)请先将下式化简,再选择一个你喜欢又使原式有意义的数代入求值.

解：原式=

8. (08山东省日照市)化简，再求值：÷，其中，．

解：原式＝　　 ……………………………2分

＝　　　　 …………………………………………3分

＝．　　　 …………………………………………………………4分

当，时，

原式＝．　 …………………………………………………6分

7. (2008新疆乌鲁木齐市)先化简，再求值：，其中．

解：原式

　　 当时，原式

6.(2008宁夏)先化简，再求值：，其中．

解：

=　　　　　　　　　　　　　　　　　　　

当时，

原式==

5. (2008云南省)已知，求的值．

解：原式 ．

　　　 　∴当时，原式．

4. (2008四川达州市)先将化简，然后请你选一个自己喜欢的值，求原式的值．

解：原式＝

　　＝

　　＝

取x＝10，则原式＝10

3.(2008湘潭市)先化简，再求值：

，其中满足.

解：

　　　　 =············································································ 3分

或 ····························································································· 5分

当时，分式无意义．

原式的值为2．······························································································ 6分

2.(2008资阳市 )． 先化简，再求值：(－)÷，其中x＝1．

解：原式=[–]×························································· 3分

=×–×

=–·································································································· 4分

=–

=··········································································································· 5分

当x=1时，

原式=····································································································· 6分

= 1················································································································· 7分