问题 解答题
证明对数换底公式:logbN=
logaN
logab
(a,b,N都是正数,a≠1,b≠1).
答案

证明:令logbN=x,则bx=N,两边同取以a为底的对数得:

logbxa
=logaN

∴x?logab=logaN

∴x=

logNa
logba

∴logbN=

logNa
logba
成立.

单项选择题
填空题

阅读下面对话,请根据所给中文正确拼写单词,使短文意思完整。每空限填一词。

Zhang Wei:Glad to meet you,Mr Xu. _1____(欢迎) to Dongyang TV Station to tell your story

                      of doing business.

Mr Xu:       Thank you. I’d like to say something that __  2___(发生)thirty years ago.

Zhang Wei:At that time,you didn’t have     3    (足够的)food to eat.

Mr Xu:       Right. So I went out to do business to make money by exchange sweets for chicken 

                      feathers,old shoes and so on. I had to get up very early every morning and travel a long

                      way on       4      (脚).

Zhang Wei:It must be a special __  5___(经历) for you.

Mr Xu:       Yes. During that time,I was’ often tired and hungry      6    (没有)anything to eat.,

                      especially on those cold winter nights…but now everything is much __    7_____(好). I 

                      own a big factory with__     8____(百) of workers. And I sell products      9___

                      (商品) make in my own factory to the world in a modern market. I’m sure my business

                      will be better and  better in the future.

Zhang Wei:How moving! Hard work makes a __  10  __ (成功) businessman. You’re really a great

                      example for the young people in Dongyang.