2022英语周报高三第18期答案

第一节Dear Mr GeorgeI am Li Hua, a volunteer of the activity"Englishi Communication to the Mountains". Now, I'm writing toexpress my sincere apology to you for not being present atthe activity to be held next Monday.The reason for my absence is that I suddenly fell illMy parents sent me to hospital, and I have to stay therefor a week. As for my volunteer work, I have asked myclassmate Tom to do it.Sincerely hoping that you can accept my apologiesYours.Li Hua

17解:(1)∵椭圆G的焦点为F1(-2√2,0)和F2(2√20),长轴长为6,∴椭圆的焦点在x轴上,c=2√2,a=3,b=√a2椭圆C的标准方程为 y2(4分)(2)设A(x1,y1),B(x2,y2)线段AB的中点为M(Io, yo)x2 9y2=9,由消去y,得10x2 36x 27=0,y=x 2(6分)∵∴x1 .18270x25·3=x 2。9=弦AB的中点坐标为(-3,3)AB|=√1 k1x1-x2=√1 k√(x1 x2)2-4x1x2(-35)-4×-52.“(10分)

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