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问题 选择题

多项式1+xy－xy²的次数及最高次项的系数分别是（   ）

A．3，1

B．2，－1

C．3，－1

D．5，－1

答案

答案：C

多项式的次数是多项式中最高次项的次数，即-xy2的次数．所以多项式1+xy-xy2的次数及最高次项的系数分别是3，-1．

故选C．

填空题

等边三角形每个角都是（    ）。
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单项选择题

Networks can be interconnected by different devices. In the physical layer, networks can be connected by (11) or hubs, which just move the bits from one network to an identical network. One layer up we find bridges and switches, which operate at data link layer. They can accept (12) ,examine the MAC address, and forward the frames to a different network while doing minor protocol translation in the process. In the network layer, we have routers that can connect two networks. If two networks have (13) network layer, the router may be able to translate between the packer formats. In the transport layer we find transport gateway, which can interface between two transport connections. Finally, in the application layer, application gateways translate message (14) . As an example, gateways between Internet e-mail and X.400 e-mail must (15) the e-mail message and change various header fields.

12（）

A.frames

B.packets

C.packages

D.cells
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