2022高二英语周报课时答案

20.【命题意图】本题考查椭圆的标准方程及其简单几何性质、直线与椭圆的位置关系,考查转化与化归思想,体现了逻辑推理、数学运算等核心素养解1()题意得=3,a+c=13+2c=分,解得a=2,b=1(3分)所以椭圆C的标准方程为+y2=1.(4分)(2)因为。△=5(3-1)41,所以直线AB的斜率k大于0.由题意得y=ka1(0,则D(-k0设B(x,ya)(6分)y=kx+1联立得方程组+2=1消去x并整理,得(4k2+1)y2-2y+1-4k2=0由1·y6=14<0,得1-4k2<0,解得k14k2+1且=4k+1①(8分)且yo(8分)易得2(2)153△BDF2(+)y3(3+1)即2k-1=5②(9分)(√3k+1)ly03(3+1)将①代入②,可得4k2+1(3k+1)(2k+1)3(3+1)则(23+12)k2-(53+10)k+33-2=0,即(k-1)[(23+12)k+(2-33)]=0,解得k1或s383-2<1(舍去),(1)分)23+12所以直线l的方程为y=x+1(12分)

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

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