题干

国家物价部门在2015年11月11日那天,对某商品在网上五大购物平台的一天销售量及其价格进行调查,5大购物平台的售价x元和销售量y件之间的一组数据如表所示:

价格x

9

9.5

10

10.5

11

销售量y

11

10

8

6

5

由散点图可知,销售量y与价格x之间有明显的线性相关关系,已知其线性回归直线方程是:y=﹣3.2x+a,则a=(   )

A:24

B:35.6

C:40

D:40.5

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答案(点此获取答案解析)

C

同类题5

    I'm Alfred. I was born with a problem in my backbone and mobility(行走能力)was a big challenge, but thanks to my teachers and friends, my school life was excellent.
    My friends and I used to sit together and have lots of fun. Whenever we got a free period, we used to start shouting or play games. I would take part in all competitions, such as poetry writing, story writing and painting and all activities like Teachers' Day or anybody's birthday and had much fun.
    My English teacher was very tall. The moment she would enter the class, we would all sit quiet and open the books. She would encourage me by giving me important assignments and also morning news to read during the assembly. She would come down and hear my English debate(辩论), which made me participate in all debate competitions.
    The same was true of my biology and science teacher. She was very nice and sweet. She would always give me extra information on the biology project. I could not go to the lab for the practicals (lessons or exams in science, cooking etc. in which you have to do or make something yourself rather than write or read about it), so she would bring the lab down and help me with the biology and science practicals and would give me excellent marks.
    My friends made me monitor and the naughty boys listen to me. My friends used to help me with my notes if I was absent. My teachers always gave me important project work and I felt proud when they patted me on the back after I finished it quickly and correctly.
I was never shouted at or made fun of or scolded(批评) by any of my friends and teachers. Today I saw the terrible punishments given to students on television news. I felt very sad.
    I really want to express my love and thanks to all my wonderful teachers and friends, without whom my school life would not have been so excellent and unforgettable. I really pray to God that each child in the world is blessed with caring teachers and wants to attend school every day.