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问题 解答题

已知n（n≥2）个点P1、P2、P3、…、Pn在同一平面内，且其中没有任何三点在同一直线上，设Sn表示过这n个点中的任意两个点所画的直线条数，显然S2=1，S3=3，S4=6，S5=10，…，试求Sn的值。

答案

解：。

填空题

截止4月15日全国已通报确诊63例人感染H7N9禽流感病例，H7N9是禽流感的一种亚型，在禽类中传播速度较快，上海等地已开始捕杀活禽.如果一只活禽，经过两轮感染后就会有36只活禽被感染，假设每轮传染中平均每只活禽传染了x只活禽，那么可列方程为                    ；n轮感染后，被感染的活禽只数为_______ _只. (用含n的代数式表示)
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单项选择题

It should go without saying that the focus of UML is modeling. However, what that means, exactly, can be an open-ended question. __(71)__ is a means to capture ideas, relationships, decisions, and requirements in a well-defined notation that can be applied to many different domains. Modeling not only means different things to different people, but also it can use different pieces of UML depending on what you are trying to convey. In general, a UML model is made up of one or more __(72)__. A diagram graphically represents things, and the relationships between these things. These __(73)__ can be representations of real-world objects, pure software constructs, or a description of the behavior of some other objects. It is common for an individual thing to show up on multiple diagrams; each diagram represents a particular interest, or view, of the thing being modeled. UML 2.0 divides diagrams into two categories: structural diagrams and behavioral diagrams. __(74)__ are used to capture the physical organization of the things in your system, i.e., how one object relates to another. __(75)__ focus on the behavior of elements in a system. For example, you can use behavioral diagrams to capture requirements, operations, and internal state changes for elements.

A．views

B．diagrams

C．user views

D．structure pictures
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