问题
选择题
若平面向量
|
答案
设
=（x，y），b
由两个向量的夹角公式得 cos180°=-1=
=
•a b |
|•|a
|b
，-x+2y
×35 5
∴x-2y=15 ①，∵
=3x2+y2
②，5
由①②联立方程组并解得x=3，y=-6，即
=（3，-6），b
故选 D．
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若平面向量
|
设
=（x，y），b
由两个向量的夹角公式得 cos180°=-1=
=
•a b |
|•|a
|b
，-x+2y
×35 5
∴x-2y=15 ①，∵
=3x2+y2
②，5
由①②联立方程组并解得x=3，y=-6，即
=（3，-6），b
故选 D．
| 完形填空。 One of the most famous movie prizes in the world is the Oscar. 1 in the United States, the Academy of Motion Picture Arts and Sciences gives Oscars to people who have done 2 the movies. There is an Oscar for the best movies of the year, another for the best actor, and Oscars for doing many other things well in the movies. Oscars are very important 3 people want to see movies that won them. They want to see actors who have won Oscars, 4 . This means that movies that have won Oscars make a lot of 5 . The Academy first gave prizes to movies 6 1927, but they were not called Oscars. That happened 7 four years. Most people think that Oscar was someone famous in the movies, but he 8 . He was no one important. He was someone that a woman called Margaret Herrick knew. She worked for the Academy and one day she saw the 9 on a table. She said, "He 10 my friend, Oscar." From that time on the prizes were called the Oscars. | ||||
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