问题 选择题
x2
a2
-
y2
b2
=1
x2
b2
-
y2
a2
=1(a>b>0)的渐近线(  )
A.重合
B.不重合,但关于x轴对称
C.不重合,但关于y轴对称
D.不重合,但关于直线y=x对称
答案

∵双曲线

x2
a2
-
y2
b2
=1的渐近线方程为y=±
b
a
x,

而双曲线

x2
b2
-
y2
a2
=1的渐近线方程为y=±
a
b
x,

∴当a>b>0时,它们的渐近线不能重合

又∵直线y=±

b
a
x关于直线y=x对称的直线是x=±
b
a
y,即y=±
a
b
x,

∴两个双曲线的渐近线关于直线y=x对称

故选:D

阅读理解

The United States of America is the most culturally diverse(多样化) country in the world in terms of culture religion, ethnicity(种族) and sexual orientation. As a combination of various races and cultures, America is home to all. The culture here is so unique that citizens can be just as proud of their original cultural heritage(遗产) as they are to be American.

What is now the US was initially inhabited(居住) by native people until the land was settled by various European groups and African slaves. Since the 20th century, the country has become a heaven for people from all over the globe(全球).

The arrival of immigrants(移民) has shifted populations from rural(农村的) areas into cities because immigrants tend to settle in urban areas. At present, 81 percent of the inhabitants in the US live in cities.

Cultural and ethnic diversity adds a unique flavor to cities that is expressed through distinct(独特的) neighborhoods, restaurants, places of worship, museums, nightlife and multicultural learning environments.

Unique musical forms, such as jazz, rock and roll, Chicano music, and the blues, grow in the US by mixing a variety of culturally distinct musical traditions to create a new form.

At the executive (行政的) level, the country is headed by a mixed­race president; two posts(职位) on the Supreme Court are held by members of the country's two largest minorities.There is also diversity in state and local governments.

Without its rich mixture of races and cultures, America would not be the nation that it is today. Founded upon the basis of equality and freedom, America acts as a stage where different cultures not only co­exist peacefully, but develop well.

小题1:According to the passage, America is a country________.

A.that welcomes people from all over the world

B.where citizens take more pride in their original culture

C.that is mostly settled by Europeans and Africans

D.where 81% of the population are immigrants小题2:Where did most people live before many immigrants came to America?

A.In the urban areas.

B.In the rural areas.

C.In the southern part of America.

D.In the northern part of America.小题3:We can learn from the sixth paragraph that________.

A.diversity(多样化) has existed in America in almost every aspect(方面)

B.most posts in American state governments are held by mixed­race people

C.equality and freedom make America a fair country

D.diversity has greatly affected the American political field小题4:What's the best title for this passage?

A.The effects of culture and diversity on America.

B.The influence of globalization on America.

C.The political development of America.

D.The bright future of America.小题5:We would most probably read this passage in a book about________.

A.science

B.history

C.culture

D.amusement

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