问题 填空题
设F1是椭圆
x2
4
+y2=1的左焦点,O为坐标原点,点P在椭圆上,则
PF1
PO
的取值范围是______.
答案

设P(x,y),则

PF1
PO
=(-
3
-x,-y)•(-x,-y)=x2+
3
x+y2=x2+
3
x+1-
1
4
x2

=

3
4
x2+
3
x+1=(
3
2
x+1)2,x∈[-2,2].

∴所求范围为[0,4+2

3
].

阅读理解

根据短文内容,选择最佳答案。

     One day an Indian went to his doctor. The doctor looked him over and said, "Medicine (药)won't help

 you. You must have a good rest. Go to a quiet place for a month, go to bed early, drink milk, walk a lot,

  and smoke (吸) only one cigar (烟) a day. "

     A month later the Indian came to see the doctor again.  "How are you?"said the doctor, "I'm glad to see

  you again. You look much younger. " "Oh, doctor,I feel quite well now!"said the Indian.  "I had a good

 rest. I went to bed early,I drank a lot of milk. I walked a lot . You certainly helped me. But you told me

 to smoke one cigar a day,and that one cigar a day almost killed (杀死) me at first. It was no joke to begin

 smoking at my age. "

1. One day an Indian ______. 

    A. wasn't feeling well    

    B. went to see a friend    

    C. felt very tired  

    D. went to his doctor and helped him

2. His doctor ______. 

    A. could not help him  

    B. was good to him    

    C. told him what to do  

    D.  was glad to see him 

3. When the Indian came to see the doctor again ______. 

    A. the Indian was younger    

    B. the doctor was not free   

    C. the Indian  felt quite well   

    D. the doctor looked him over

4. The Indian told the doctor______. 

    A. he liked doing all those things    

    B. he almost killed him    

    C. to smoke one cigar a day  

    D. one cigar a day was very difficult at the beginning

5. From this story we can guess______. 

    A. the Indian was not a young man    

    B. the doctor was very interesting    

    C. the doctor was a good one   

     D. the Indian didn't smoke at first

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