【简答题】已知椭圆 E: x 2 a 2 + y 2 b 2 =1(a>b>0) 的长轴长是短轴长的两倍,且过点C(2,1),点C关于原点O的对称点为点D. (I)求椭圆E的方程; (Ⅱ)点P在椭圆E上,直线CP和DP的斜率都存在且不为0,试问直线CP和DP的斜率之积是否为定值?若是,求此定值;若不是,请说明理由: (Ⅲ)平行于CD的直线l交椭圆E于M,N两点,求△CMN面积的最大值,并求此时直线l的方程.
【简答题】Jack: Hey. Gina. Do you want a cup of tea? Gina: No thanks. _______1_______. Jack: Really? Where are you going? Gina: I'm going to play baseball. Do you want to come? Jack: Sorry, I can’t. _________2_...