设函数f（x）的定义域为D，若函数f（x）满足条件：存在[a，b]⊆D，使f（x）在[a，b]上的值域是[2a，2b]，则称f（x）为“倍扩函数”，若函数f（x）=log2（2x+t）为“倍扩函数”，_刷题宝

题干

设函数f（x）的定义域为D，若函数f（x）满足条件：存在[a，b]⊆D，使f（x）在[a，b]上的值域是[2a，2b]，则称f（x）为“倍扩函数”，若函数f（x）=log₂（2^x+t）为“倍扩函数”，则实数t的取值范围是（）

A： $(\infty, - \frac{1}{4})$

B： $(- \frac{1}{4}, 0)$

C： $(- \frac{1}{4}, 0$

D： $- \frac{1}{4}, 0)$

上一题下一题 0.0难度选择题更新时间:2010-04-22 02:08:01

答案(点此获取答案解析）

B

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阅读理解。

Billy doesn't go to school today. He wants to read a storybook. His brother bought(买)one for him yesterday. (1) Billy likes this book.

Billy goes to his bookcase. The book is not there. Billy looks under the bed. but it isn't there. (2) No, it isn't. He looks inside his schoolbag,but he still(仍然)can't find the book. Billy isn't happy. (3) Billy goes to the living room(客厅). His mum is reading a book on the sofa.

" (4) "asks Billy.

"Which one?"says his mum.

"The one about a dog. "says Billy.

"It's in your brother's bedroom. "says his mum. "I found it on the table after breakfast. I thought it was his book. (5) "

"Great! Thanks, Mum, "says Billy.

根据材料内容, 从方框中选择合适的句子填入文中空缺处, 使材料完整、通顺。

A. Is it under the chair?

B. Does he lose the book?

C. It is about a nice dog.

D. So I put it in his bookcase.

E. Mum, did you see my storybook?

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