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排列、组合是高考必考题.它联系实际,生动有趣,但题型多样,思路灵活,比较抽象,容易发生重复和遗漏现象.选择灵活的统计策略是正确解决排列组合问题的关键.下面通过典型问题,介绍几类常见解法. 一位异则分元素(或位置)“地位”不相同时,不可直接用排列、组合数公式,则要根据元素(或位置)
Arrangements and combinations are required for college entrance examinations. It is practical, interesting and interesting. However, the types of questions are varied, the ideas are flexible, and they are relatively abstract. They are prone to duplication and omissions. Choosing a flexible statistical strategy is the key to correctly solving the permutation and combination problems. Problems, introduce several types of common solutions. When an element is different (or position) “status” is not the same, can not be directly used to arrange, combine the number formula, according to the element (or position)