已知向量a与b的夹角为120°,且|a|=2,|b|=5,则(2a-b)•a=_

题型:填空题

问题:

已知向量
a
b
的夹角为120°,且|
a
|=2,|
b
|=5,则(2
a
-
b
)•
a
=______.
考点:向量数量积的运算
题型:填空题

There was a boy and his family was very rich. One day his father took him on a trip to a place. He wanted to show his son how poor people were there. They spent several days on a farm. There were many poor families living on the farm.

On their way home, the father asked the son, “How was the trip?” “It was great, Dad,” the son answered. “Did you notice how poor people were there?” asked his father. “Oh, yes,” said the son. “So, tell me,” said his father. The son said, “Well, we have one dog and they have four. We have a pool in our garden, while they have a river that has no end. We have expensive lanterns (灯), but they have stars above their heads at night. We have only a small piece of land to live on, while they have the endless fields. We buy our food, but they grow theirs. We have high walls around our houses to protect us, but they don’t need walls, because their friends will protect them.”

The father had nothing to say. Then the boy added, “Thank you, Dad, for letting me see how poor we are.”

小题1: The father wanted to show his son ________.

A.how people on the farm worked

B.how poor people were on the farm

C.how beautiful the farm was

D.how far it was from the city to the farm小题2:How often did they go to the farm?

A.Once a week.

B.Twice a month.

C.Every year.

D.The writer doesn’t tell us.小题3:When the father asked the son how the trip was, the son thought it ________.

A.great

B.tiring

C.terrible

D.boring小题4:According to the boy, people on the farm can see ________ at night.

A.expensive lanterns

B.a lot of cars

C.stars above their heads

D.many horses小题5: Which of the following is TRUE, according to the passage?

A.The boy was from a very poor family.

B.The father and the son spent several weeks on a farm.

C.People on the farm have high walls around their houses.

D.The boy thought that people on the farm lived a happy life.

题型:填空题

负载作三角形联接时的相电流,是指相线中的电流。

题型:填空题

每m3空气中饱和水分含量及对应的饱和水蒸气压力仅与温度有关.当压力越高,空气的重度()。

A.越大

B.越小

C.不变

D.无法比较

题型:填空题

地铁在运营时司机可随时根据客流情况将自动驾驶模式转化成ATP手动驾驶模式。

题型:填空题

女性,51岁,近2天出现右上腹持续性疼痛,阵发加剧,并向右腰背放射,高热,皮肤及巩膜黄染,大便发白,小便黄。可能的诊断是

A.消化性溃疡穿孔

B.急性黄疸性肝炎

C.急性胰腺炎

D.急性胆囊炎,胆结石

E.肝破裂

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