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要使学生掌握好解“选择题”的常用方法,最关键的地方是讲清“透择题”常用解法的逻辑依据。“选择题”的解法分两大类:一类是直接解法;另一类是间接解法。直接解法学生比较熟悉,下面举例说明各种具体间接解法的逻辑依据和应注意的地方。(本文中的选择题都是指的一元选择题,并且选例都是近几年全国高考题或部份地区的高考题和国内外数学竞赛题。) 一、特殊值法: 在应用特殊值法解一元选择题时,实质上从逻辑上来讲是一种排除法,四个选择支中排除了三个
To enable students to master the common methods for solving the “choice questions”, the most crucial point is to clarify the logical basis of the common solution to the “selective questions”. The solution to “multiple choice” is divided into two categories: one is direct solution; the other is indirect solution. Direct solution students are more familiar with the following examples illustrate the logical basis of various specific indirect solutions and should pay attention to. (The multiple-choice questions in this article refer to the single-choice questions, and the selection examples are the national college entrance examination questions or the local college entrance examination questions and mathematics competition questions at home and abroad in recent years.) First, the special value method: in the application of special values When solving a single-choice question, it is logically an exclusion method. Three of the four options exclude three