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
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