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一注重基础,依据课本,贴近生活以课本中的例题或习题为依据,通过改变问题的背景、基础知识的变式和拓展,成为立意新、情境贴近实际生活:设问巧、并赋予时代气息的问题.例1一接待中心有A、B、C、D四部热线电话,已知某一时刻电话A、B占线的概率均为0.5.电话C、D占线的概率均为0.4.各部电话是否占线相互之间没有影响,假设该时刻有ξ部电话占线,试求随机变量ξ的概率分布和它的期望.
Focusing on the basics, based on textbooks, and being close to life based on examples or exercises in textbooks, through changing the background of the problem, the variation and expansion of basic knowledge, it becomes a new concept and the situation is close to real life: it is ingenuity and it is endowed with the flavor of the times. Problem 1. Example 1 A reception center has A, B, C, and D hotlines. It is known that the probability that telephones A and B are busy at a certain moment is 0.5. The probability that telephones C and D are busy is 0.4. There is no influence between busy lines. Assume that there is a busy phone at this moment, try the probability distribution of the random variable 和 and its expectation.