高一新生学习了逻辑知识 ,利用反证法证明一个数学命题时 ,要涉及到对一些量词的否定 .如“都是”、“不都是”、“都不是”、“至多”、“至少”、“唯一”等等 ,学生往往感到困难 .有的书上总结为 :“都是”的否定是“不都是” ,而不是“都不是” ;“都不是”的否定既不是“ When a freshman student learns logical knowledge and uses proof-of-proof to prove a mathematical proposition, it involves negating some quantifiers, such as “all”, “not all”, “not all”, “at most”, “at least”, “Single” and so on, students often feel troubled. Some books are summarized as follows: The negative of “all” is “not all” but not “not”; the negation of “not both” is neither "