【摘要】 通过“换元”“试验”、“一题多解”等方法 ,解决“排列组合应用题”中何时使用加法原理、何时使用乘法原理、怎样进行分类、何时需要分类等难点问题更多还原

【Abstract】 By using the methods of "substitution”,"experiment”,"many solutions to one problem”,this paper solves the applied problems of permutations and combinations,and also solves the difficult prblems such as when to use addition principle,when to use multiplication principle,and when and how to classify.更多还原