Question

若双曲线－=1的实轴长、虚轴长、焦距成等差数列，则双曲线的离心率是

A.2                                                                 B.3

C.                                                                      D.

Answer 1

D

解析:

由2b=a+c得4b²=a²+2ac+c²,

即3c²－2ac－5a²=0,∴3e²－2e－5=0.∴e=.