25 A.Invest on real estate properties. B.Spend 30% of it in stocks and shares. C.Put all of it in low-risk investment. D.Invest on their children's education.
【简答题】已知与向量 e =(1, 3 )平行的直线l 1 过点A(0,-2 3 ),椭圆C: x 2 a 2 + y 2 b 2 =1(a>b>0)的中心关于直线l 1 的对称点在直线x= a 2 c (c 2 =a 2 -b 2 )上,且直线l 1 过椭圆C的焦点. (Ⅰ)求椭圆C的方程; (Ⅱ)过点B(-2,0)的直线l 2 交椭圆C于M,N两点,若∠MON≠ π 2 ,且( OM ? ON )?si...