若双曲线x2a2-y2b2=1的渐近线方程为y=±32x，则其离心率为（） A．_爱下问搜题

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问题选择题

若双曲线

x2

a2

-

y2

b2

=1的渐近线方程为y=±

3

2

x，则其离心率为（　　）

A．

13

2

B．

13

3

C．

2

13

或

3

13

D．

13

2

或

13

3

答案

依题意可知

b

a

=

3

2

∴a=

2

3

b

∴c=

b2+

4

9

b2

=

13

3

b

∴e=

c

a

=

13

2

故选A

选择题

—May I speak to Mr Smith?
—Sorry, he ____ Australia. But he ____ in two days.

A. has been to; will come back
B. has gone to; will be back
C. has been in; would come back
D. is leaving for; doesn't come back

单项选择题

治疗疳疾常用的经外奇穴是：（）

A.四缝

B.八邪

C.二白

D.定喘

E.太阳