2021-2022英语周报高一新课程第40期答案

Li Hua第二节There was a phone number on the flyer. My dadcalled it and someone answered it was a lady. My dadasked whether she was the one who put out the flyers. Shesaid "Yes! with excitement and told us Coby, who wasvery dear to her, had been gone days before. Then we toldher that we had her puppy and we would take him to her.She told us her address at once: then we went to itWe found the lady's house, and then we knocked on ihe door. A lady opened the door, and when she saw thepuppy, she screamed with joy. We handed her the puppyfeeling proud. She wanted to give us a reward for takingcare of her puppy for her, but we said it was OK becausewe were really happy to help. So we went home tired butcontent, telling my mom the whole thing My familybecame friends with the lady, and we were all happy.

20.(1)解:由题意知,c=3,则a2=b2+31分当PF1⊥F1F2时,PF2|=2PF1【高三数学试卷·参考答案第3页(共5页)理科】20-04-6030因为PF:+1PF1|=2a,所以PF1=3a,由得6=6.…………………4分a2=b2+3.所以椭圆C的标准方程为+=1.…5分(2)证明:由题意可得直线l的斜率存在当直线l的斜率不为0时,设直线l的方程为x=my-4,M(x,y),N(x2,y2),r=my-4.则M(x1,-y),联立方程组整理可得(3+2m2)y2-16my+14=014则y1+y2=3+2m2…y一3+2m2由△=(-16m)2-4×(3+2m2)×14>0,得m2>8分直线NM的方程为y-y2=2+2(x-x2)整理可得y二千边,一五边十边二一16(y2-y1)(3+2m2)(x+).………………………………………………………10分当x=一9时,y=0,即直线M过定点(-,0)分当x=-元时,y=0,即直线NM过定点(--,0)11分当直线l的斜率为0时,M,M重合,直线NM显然也过点(9综上所述,直线NM过定点(-2,0)12分评分细则【1】第(1)问解法二:由题意知,c=/3,即a2=b2+31分设点P的标为(一,y),则7b得y=a即PF/=2q:……因为2a=PF1+PF2,PF2|=2|PF1|,所以2a2=3,…4分所以a2=9,b2=6,故椭圆C的标准力程为+÷=15分【2】第(2)问中,若未考虑斜率为0的情况,扣1分;【3】第(2)问中,直线l的方程也可以设为y=k(x+4),参照上述步骤酌情给分

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