已知OA=(2,1),OB=(t,-2),OC=(1,2t).(1)若|AB|=

题型:解答题

问题:

已知
OA
=(2,1),
OB
=(t,-2),
OC
=(1,2t)

(1)若|
AB
|=5
,求t.
(2)若∠BOC=90°,求t.
(3)若A、B、C三点共线,求t.
考点:向量模的计算
题型:解答题

对境外竞标或收购项目,应在投或对外正式开展商务活动前,向( )送书面信息报告。

A.国务院

B.商务部

C.国家发展改革委员会

D.国务院对外贸易主管部门

题型:解答题

用A+、B-、C2-、D、E、F、G和H分别表示含有18个电子的八种微粒(离子或分子),请回答:

(1)A元素是_______、B元素是_______、C元素是_______(用元素符号表示)。

(2)D是由两种元素组成的双原子分子,其分子式是__________。

(3)E是所有含18个电子的微粒中氧化能力最强的分子,其分子式是__________。

(4)F是由两种元素组成的三原子分子,其分子式是_______,电子式是__ ______。

(5)G分子中含有4个原子,其分子式是__________。

(6)H分子中含有8个原子,其分子式是__________。

题型:解答题

Early in the 18th century, Captain Cook, a famous explorer of Australia, unexpectedly caught sight of an unusual animal during his first visit to Australia. The animal had a large mouse like head and jumped along on its large legs. To his great surprise, the unusual animal carried its young in a special pocket of flesh. Captain Cook pointed to the animal which was eating grass in the distance and asked his native guide what the animal was referred to. The guide seemed not to know that he was pointing at and finally said “Kang-a-roo”, but their requests were met with puzzled looks of the native people. Before long they got to discover that the native guide who made the answer to Cook’s question really meant, “I don’t know what you pointing at. “ Funny enough, the name “ Kang-a-roo”, stuck and it is still in use today.

小题1:Which of the following sentences best expresses the main idea?

A.captain Cook’s guide made a joke.

B.Native Australians could not speak English in Cook’s time.

C.Some words have rather funny origins (起源).

D.Captain Cook was a lover of wild animals.小题2:When the native guide said “Kang-a-roo ”, he really meant “ ______”

A.Ah, it is a special kind of animal

B.I wonder what you have said

C.What do you mean by pointing at that animal?

D.I have no idea of what you are referring to.小题3:We can infer from this passage ______.

A.we should learn many different languages

B.Captain Cook made a mistake in understanding

C.Captain Cook was a foolish explorer

D.the importance of a language in common

题型:解答题

环境问题通常分成几个决策层次?它们各自的目标和任务是什么?

题型:解答题

指出下面哪些行为特点的出现标志着酒精依赖的形成()?

A.经常喝醉

B.强制性用酒

C.戒断症状

D.出现明显的耐受

更多题库