已知limn→∞(2n2n+1-an-b)=2，其中a，b∈R，则a-b=___

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问题填空题

已知

lim

n→∞

(

2n2

n+1

-an-b)=2，其中a，b∈R，则a-b=______．

答案

由

lim

n→∞

(

2n2

n+1

-an-b)=

lim

n→∞

(2-a)n2-(a+b)n-b

n+1

可得，

2-a=0

a+b=-2

解可得，a=2，b=-4

所以a-b=6

故答案为：6

阅读理解

阅读理解。

Mr. Green works in a hospital. The hospital is near the bus stop only three minutes'

(分钟) walk. Every day Mr. Green goes to work by bus. This is the bus timetable. Read it

carefully and then answer the questions below.

1. We can see _____ stops from the bus timetable.[ ]

2. It takes (花费) Mr. Green _____ minutes from Post Office to Blue Bridge.[ ]

3. ____ can get to the library at seven twenty-five. [ ]

4. Bus4 gets to the Blue Bridge at _____. [ ]

A. six thirty-five

B. seven five

C. seven thirty-five D.eight fifteen

5. If (如果) Mr. Smith wants to get to the hospital at eight o'clock, he can take _____. [ ]

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判断题

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