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第一环节:字母表示任意数展示:a+b=b+a。提问:它是谁?这里的a和b代表什么?生:代表两个数。(板书:数)举个例子。生举例如:1+2=2+1。除了表示这两个数以外,还可以表示怎样的数?师:也就是说这里的字母不仅表示数,还表示任意数。那么字母除了表示任意数以外,字母还可以表示怎样的数呢?今天这节课我们一起来研究“用字母表示数”。
The first link: Letters that any number of shows: a + b = b + a. Question: Who is it? What does a and b mean here? 生: Represents two numbers. (Blackboard: number) For example. For example: 1 + 2 = 2 + 1. In addition to these two numbers outside, you can also say what kind of number? Teacher: In other words, the letters here not only that number, but also that any number. So how many letters can represent in addition to any number? Today in this class, we study “in alphabetical order ”.