Carol Kornhaber and her husband don’t have too much financial pressure because ___________. A) they have parents who are rich B) they don’t have children to feed C) they both have a high salary D) they both have work and they are thrifty
【简答题】点M在椭圆 x 2 a 2 + y 2 b 2 =1 (a>b>0)上,以M为圆心的圆与x轴相切于椭圆的右焦点F. (I)若圆M与y轴相交于A、B两点,且△ABM是边长为2的正三角形,求椭圆的方程; (Ⅱ)已知点F(1,0),设过点F的直线l交椭圆于C、D两点,若直线l绕点F任意转动时,恒有|OC| 2 +|OD| 2 <|CD| 2 成立,求实数a的取值范围.