我过电视频道的划分是这样的：1-12频道,波长是5.71-1.37m；13-48频道,波长是0.633-0.378m.它

解题思路：解答本题可根据公式c=λf计算，用此公式分别算出这两个波长对应的频率，从而就知道了它接收的频率范围．

由c=λf得：f=[c/λ]
波长为1.37m的频率：f₁=[c
λ1=
3×108m/s/1.37m]=218978102Hz
波长为5.71m的频率：f₂=[c
λ2=
3×108m/s/5.71m]=52539404Hz
故答案为 52539404，218978102

点评：
本题考点： 波速、波长和频率的关系．

考点点评： 本题考查了波速、波长和频率的关系，要会用这三个的关系进行简单的计算．

解题思路：电磁波的速度是3×10⁸m/s，根据波长、频率、波速的关系式c=λf就可以计算出频率．

电磁波的波速c=3×10⁸m/s，
∵c=λf，
∴波长为1.37m的频率：f₁=[c
λ1=
3×108m/s/1.37m]=218978102Hz≈219MHz；
波长为5.71m的频率：f₂=[c
λ2=
3×108m/s/5.71m]=52539404Hz≈52.5MHz．
故答案为：219；52.5．

点评：
本题考点： 波速、波长和频率的关系．

考点点评： 本题考查了波速、波长和频率的关系，会用这三个的关系进行简单的计算，属于基础知识的考查．

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Dear Sir,
I checked in your hotel on (日期）.During my staying there,something made me feel uncomfortable:
1.When I checking in,the receptionist complained that I didn't
make a reservation.But,is it neccessary to make reservation for each time?
2.In the guest room,some facilities had problems.Some lights couldn't on; There is no hot water in the washroom.And TV channels are too limited.
3.The service for guest room was too slow,and their staff was in a bad service attitude.
As a hotel,it shouldn't has problems as I told above.Each hotel hope to give a good impression to the guests.So I hope something can be changed for your hotel and for a improvement.
署名

解题思路：一定会发生的事件为必然事件．

A，B，D选项中，可能发生也可能不发生，是随机事件，不符合题意；
是必然事件的是：通常情况下，抛出的石块会下落，符合题意．
故选C．

点评：
本题考点： 随机事件．

考点点评： 解决本题要正确理解必然事件、不可能事件、随机事件的概念，理解概念是解决基础题的主要方法．用到的知识点为：必然事件指在一定条件下一定发生的事件；不确定事件即随机事件是指在一定条件下，可能发生也可能不发生的事件．

(1)依题意有第k次播放了k+(ak-1-k)=ak-1+k.1分
　　因此ak=ak-1-(ak-1+k)ak-1=k+ak.3分
　　(2)a0=1+a1=1+(2+a2)= 4分
　　1+2×+()2a2=……=
　　1+2×+3×()2+…+x×()x-1()xax.
　　∵ax=0,∴y=1+2×()+3×()2+…+x×()x-1.8分
　　用错位相减法求和得y=49+(x-7).10分
　　∵y∈N,∴x-7=0,即

how to choose and keep a brand column of BS in the condition of vision devided Media
abstract
with the development of science and technology and Economic level ,the channals and medias are more and more,which devides the media bunissness in detial.so build a brand colum placed onto a board or committee.this paper analyses the reason and behavior for media are devided a by analysing lots of theory of management of media ,facts and conbined with the current views and measures be taken in practice.
then points out the opportunity and threat bs faced.
at last,gives strategy for chosing and keeping brand colums and by analysing the case of chosing and keeping brand colums explains the probleily measure With a view to offer a reference to brand colum of bs and other tv channals on build brand colums.
纯手工,那里不合适 ,hi wo