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问题 解答题
已知双曲线C的方程为：
x2
9
-
y2
16
=1
（1）求双曲线C的离心率；
（2）求与双曲线C有公共的渐近线，且经过点A（-3，2
3
）的双曲线的方程．
答案

（1）由题意知a2=9，b2=16，

所以c2=a2+b2=25，

则a=3，c=5，

所以该双曲线的离心率e=

c
a
=
5
3
．

（2）根据题意，则可设双曲线的标准方程为

x2
9
-
y2
16
=λ，（λ≠0）；

又因为双曲线经过点A（-3，2

3
）

代入方程可得，λ=

1
4
；

故这条双曲线的方程为

4x2
9
-
y2
4
=1．

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Do animals have a culture What do we mean by "culture" Lately social scientists have begun to ask if culture is found just in humans, or if some animals have a culture too. When we speak of culture, we mean a way of life a group of people have in common. Culture includes the beliefs and attitudes we learn. It is the patterns of behavior that help people to live together. It is also the patterns of behavior that make one group of people different from another group.
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