英语周报2022-2022七年级18答案

第二节参考范文The girl's mother told Kelly that they were moving to another city. After that they could no longer run thefairy garden. She had reached an agreement with the community that planned to turn it into a park for local residents to relax in. But her daughter did not want to leave the garden, and she had cried several times. She waseven more unwilling to leave her dear fairy. Her mother wanted Kelly to meet her daughter personally. But shewasn t sure how to make her daughter happy.The girl's mother preferred Kelly to act as a fairy to say goodbye to her daughter. Kelly accepted thegirls mothers request. Then they agreed on a time and a place to meet. On the day of the meeting, Kelly ap-peared in front of the girl dressed like a fairy. The little girl was surprised and delighted to see her. They joinedhands and started dancing. She chatted excitedly with Kelly for a long time. Kelly gave her many gifts that sheliked. The girl made Kelly promise that Kelly would visit her often.

12.(1)由椭圆的离心率为,得a2=2(a2-b2)又当y=1时因此椭圆C的方程为(2)设A(),B(联立得2得(2k2+1)x2+4kmx+2m2-4=0,由△>0得m2<4k2+2,(兴)4km2m且2k+1,因此yZkm所以D2k2+12k2+12km又N(0,-m),所以|ND|22k2+12k2+1整理得|ND/24m2(1+3k2+k4)(2k2+1)2因为|NF所以D4(k4+3k2+1)8k2+3NF|2(2k2+1)2(2k2+1)2令t=8k2+3,t≥3,故2k2+1所以ND/2NF2(1+1)2=1+-1616t+-+2令y=t+所以y=1-1当t≥3时,y>0从而y-t十在[3,十∞)上单调递增,因此1+等号当且仅当t=3时成立,此时k=0所以I NFI由(*)得-√2

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