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问题 问答题

已知A，B为3阶矩阵，且满足2A-1B=B-4E，其中E是3阶单位矩阵．
(1)证明：矩阵A-2E可逆；(2)若

，求矩阵A．

答案

参考答案：[解] (1)由2A-1B=B-4E左乘A知AB-2B-4A=0．
从而(A-2E)(B-4E)=8E，或


故A-2E可逆，且


(2)由(1)知A=2E+8(B-4E)-1．
而


故


单项选择题

财产保险对于保险标的的保障功能表现为（）。

A．经济补偿

B．经济给付

C．合同约束

D．货币支付

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单项选择题

The development of e-commerce may well bring the world into a brand new era of "electronic currency". At the moment, (51) areas in Europe, the United States and Asia have already started studying the possibility of an electronic currency. Electronic currency is not only about currency. It (52) to an entire finance system on the Net. It includes a virtual numeric currency, an electronic system of withdrawals, transfers and loans, and (53) cards of all shapes and sizes. The (54) of an electronic currency system implies the emergence of "virtual banks" and "virtual enterprises". Actually, the first virtual bank appeared in the US in 1995. (55) it is a small and insignificant bank, it represents the trend of the future. In time to come, we may even have to (56) the familiar paper currency.

As the Net pushes the economy (57) rapidly, the economy is also bringing the Net market forward, resulting in the Internet itself becoming the world’s largest emerging market. Of course, this is just the beginning. Although there are many companies which made huge profits (58) in the Internet market, they tend to be small companies. To date, most companies are making losses. The competition in the knowledge-based economy will also be more (59) This will definitely promote (60) and more efficient cooperation.

52().

A.bridges 

B.camps 

C.refers 

D.casts
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