复习提要1.本单元知识内容主要有:加法原理和乘法原理;排列、排列数公式;组合、组合数公式、组合数的两个性质;二项式定理、二项展开式的性质.2.加法原理和乘法原理,是排列组合的基础与核心,不仅是排列数公式与组合数公式的推导依据,而且是解决排列、组合问题的基本思想方法.在应用加法原理时,要注意“类”与“类”之间的独立性,在应用乘法原 Review summary 1. The content of this unit is mainly composed of the principle of addition and multiplication; the formula of arrangement and arrangement of numbers; the nature of combination, combination number formula and combination number; the nature of binomial theorem and binomial expansion. The principle of addition and principle of multiplication are the basis and core of permutation and combination. It is not only the derivation basis for the formula of the permutation number and the formula of the combination number, but also the basic idea method for solving the problem of permutation and combination. When applying the principle of addition, attention should be paid to the “class”. Independence from “class” in applying multiplication original