试题与答案

在等差数列{an}中,a1>0,a2012+a2013>0,a2012•a201

题型:选择题

题目:

在等差数列{an}中,a1>0,a2012+a2013>0,a2012•a2013<0,则使Sn>0成立的最大自然数n是(  )

A.4025

B.4024

C.4023

D.4022

答案:

∵等差数列{an},首项a1>0,a2012+a2013>0,a2012•a2013<0,

∴a2012>0,a2013<0.

假设a2012<0<a2013,则d>0,而a1>0,可得a2012=a1+2011d>0,矛盾,故不可能.

再根据S4024=

4024(a1+a4024)
2
=2012(a2012+a2013 )>0,

而S4025=4025a2013<0,

因此使前n项和Sn>0成立的最大自然数n为4024.

故选:B.

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题型:阅读理解

Popular breakfast foods in the United States, as in many other countries around the world, include coffee, milk , juice, eggs, and bread. Some other breakfast items served in the United States are thought by many to be traditionally American. However, they actually come from other cultures.

A very popular breakfast food in America is the pancake--- a thin , flat cake made out of flour and often served with maple syrup. The idea of the pancake is very old. In fact, pancakes were made long ago in ancient China.

Bagels, a round thick bread with a hole in the middle , are also popular for breakfast in America. Polish people in the late 1600s came up with the idea for the first bagels and this new kind of bread soon took off across Eastern Europe.

In the late 1800s, thousands of Jews from Eastern Europe travelled to the United States and brought the recipe for bagels with them. Today, New York bagels are said to be the best in the world. Many people have them with cream for breakfast on the go.

Doughnuts (usually spelled “donut” in the United States) came from France. They were served to American soldiers in France in the World War Ⅰ. After the war, American soldiers asked cooks in the United States to make doughnuts for them. Now , served with coffee, they are a very popular breakfast food across the United States.

小题1:This reading is mainly about ________

A.famous places to eat breakfast.

B.why people in the United States eat breakfast

C.the most popular types of pancakes in the United States

D.the history of popular breakfast foods in the United States.小题2:The oldest breakfast food in the passage is ______

A.the pancake

B.the bagel

C.the doughnut

D.The passage doesn’t say.小题3:Which sentence is true for both bagels and donuts?

A.They both came from Europe

B.They are both easy to make

C.They are both sweet

D.people in New York make them best小题4:Who brought bagels to America?

A.Polish people

B.Jewish People

C.Chinese People

D.American soldiers小题5:Who served donuts to American soldiers during World War Ⅰ?

A.French people

B.Jewish people

C.other American soldiers

D.cooks from the United States.

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