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问题 填空题
已知
a
=（-1，1），
b
=（2，x2-x），若向量
a
与向量
b
的夹角为钝角，则x的范围为______．
答案

因为向量

a
与向量
b
的夹角为钝角，

所以

a
•
b
=-1×2+1×(x2-x)＜0，

即（x-2）（x+1）＜0解之可得-1＜x＜2，

由-1×（x2-x）-1×2=0，可得x2-x+2=0，

△＜0，此方程无解，故

a
与向量
b
不会反向，

故x的范围为：（-1，2）

故答案为：（-1，2）

单项选择题

Anthropology is the study of human beings as creatures of society. It (1) its attention upon those. physical characteristics and industrial techniques, those conventions and values, which (2) one community from all others that belong to a different tradition.

The distinguishing mark of anthropology among the social sciences is that it includes for serious study other societies (3) our own. For its purposes any social (4) of mating and reproduction is as significant as our own. To the anthropologist our customs and those of a New Guinea tribe are two possible social schemes for (5) a common problem, and in so far as he remains an anthropologist he is (6) to avoid any weighting of one (7) the other. He is interested in human behavior, not as it is shaped by one tradition, our own, but as it has been shaped by any tradition (8) He is interested in a wide (9) of custom that is found in various cultures, and his object is to understand the way in which these cultures change and (10) , the different forms through which they express themselves and the (11) in which the customs of any peoples function in the lives of the (12) .

Now custom has not been commonly regarded as a (13) of any great moment. The inner workings of our own brains we feel to be uniquely (14) of investigation, but custom, we have a way of thinking, is behavior at its most commonplace. (15) , it is the other way round. Traditional custom is a mass of detailed behavior more astonishing than (16) any one person can ever evolve in individual actions. Yet that is a rather (17) aspect of the matter. The fact (18) first rate importance is the predominant role that custom (19) in experience and belief, and the very great varieties it may (20)

18（）

A.in

B.of

C.at

D.to
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问答题 简答题

简述企业外部团队文化竞争力建设的方式。
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