问题 填空题
若(2
x
-
1
x
n的展开式中所有二项式系数之和为64,则展开式的常数项为______.
答案

因为(2

x
-
1
x
n的展开式的二项式系数之和为64,所以2n=64,所以n=6,
由二项式定理的通项公式可知 Tr+1=
Crn
(2
x
6-r(-
1
x
r=26-r(-1)r C
 r6
x3-r
当r=3时,展开式的常数项为:23(-1)3C
 36
=-160.
故答案为:-160.

选择题
阅读理解

There are many types of reports.A report is simply an account of something that has happened.The commonest are news reports.We get them in newspapers,over radio and on television.Sometimes cinemas also show us newsreels.

The main purpose of a newspaper is to provide news.If you examine a newspaper closely,you will find that there are all types of news:accidents,floods,fires,wars,fashions(服装),sports,books,etc.The news covers everything that happens to people and their surroundings.Sometimes there are news items which are very amusing.

A news report is usually very short,except when it is about something very important,but it contains(包含) a lot of information.It is also written in short paragraphs.The first paragraph is in fact a summary(总结) of the news item.It gives all the necessary information,what,when,where,how and why.The other paragraphs give full details of the subject.There may also be interviews with people.The words actually spoken by them are within inverted commas(引号).

Often there are photographs to go with the news to make it more interesting.

小题1:The easiest way to get today’s news is_________.

A.to go to the cinema

B.to watch a color TV

C.to read today’s newspapers

D.to listen to the music over radio小题2:Newspapers sell well mainly because_________.

A.they cost very little

B.they are easy to get

C.they have got pictures to go with the news

D.they provide all sorts of news in them小题3:This passage mainly talks about _________.

A.different types of reports

B.news reports

C.happenings to people and their surroundings

D.the length of a news reports