英语周报27期2022答案

19.(本小题满分12分)(I)由题意得,e=C=√一,∴a=2b;…………分不妨设直线l1的方程为bx qy-ab=0,即x 2y-2b=0,…2分原点O到直线4的距离d=2b=25,解得b=1,…4分√5-5r∴椭圆C的标准方程为 y2=1.分(Ⅱ)由题意得,直线l的斜率存在且不为0,设直线l的方程为y 1=k(x-2),即y=kx-2k-1,M(x,y),N(x2,y2),y=lx-2k-1联立x2整理得( 4k2)x2-8(2k 1)x 4(2k 1)2-4=0,4(2k 1)2-4△>0,x x21 4k21 4k2………8分记直线AM的斜率与直线AN的斜率分别为k,k则k k2y1-1,y2-1(y1-1)x2 (y2-1)x≈(k-2k-2)x (kx2-k-22x2(k 1x x)2(k 1)8k(2k 1)6(k1) 1)(2k 4(2k 1)2-416(k 1)1 4k即直线AM的斜率与直线AN的斜率之和为定值-112分

第一节短文改错(共10小题;每小题1分,满分10分)One day, my Spanish teacher asked if I could stay after class for a minute, that got me nervous asI thought I was in the trouble for something. It turned out she saw my paperwork and realize I was on the③3 realizedboard of the Key club. She told me that her son, Abraham, was autistic(自闭症的) but his doctorhad suggested he join a service club to help with her socialization. She asked if it would be impossiblefor me to speak with the rest of the board of letting abraham joinI immediately said I would, and the rest of the board enthusiastic about Abraham: at any activitywe did they all encouraged him, sat with him, and chatted with him, made sure he was having thebest time. It was real beautiful to seereally

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