【简答题】完形填空。 Mr. Black works 1 Mrs White. She is old, fat and rich (富有). He works in her garden. Mrs White doesn't know 2 about the garden, but she usually tells him to do this or 3 that. This makes M...
【简答题】已知向量 OA =(2 2 ,0),O是坐标原点,动点 M 满足:| OM + OA |+| OM - OA |=6. (1)求点 M 的轨迹 C 的方程; (2)是否存在直线 l 过 D(0,2)与轨迹 C 交于 P、Q 两点,且以 PQ 为直径的圆过原点,若存在,求出直线 l 的方程;若不存在,说明理由.