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列方程解应用题是初中数学中的一个难点,学生在遇到已知数与题中要求的未知数之间的关系不明显时,列方程感到特别困难,为突破这个难点,我教给学生一种方法叫“参数过渡法”,下面就来介绍这种方法。一、什么叫列方程的“参数过渡法”让我们先来看一个问题。例1、A、B两站每隔相同的时问相向发出一辆汽车且它们的速度相同。A、B之间有一个骑自行车的人,发觉每隔12分钟从后面追来一辆汽车;每隔4分钟迎面开来一辆汽车,问A、B两站每隔几分钟发车一辆? 分析:这是一个行程问题,一般可以应用s=vt的关系式来列方程,但题中的已知数和要求的未知数都是时间,没有路程,也没有速度,无法用代数来表示三者之问的关系,因而必须引进辅助未知数(即参数),故设每隔x
The problem of solving equations of equations is a difficult point in mathematics of junior high school. When students encounter the unknown between the known number and the unknown number in the question, the equations are particularly difficult. To overcome this difficulty, I teach the students a This method is called “parameter transition method”. Here we introduce this method. First, what is the “parameter transition method” of the column equation Let us first look at a problem. Cases 1, A and B sent two cars opposite each other at the same time and they had the same speed. Between A and B, there is a cyclist who finds a car chased from the back every 12 minutes. He opens a car every 4 minutes and asks A and B stations to start every few minutes. Analysis: This is an itinerary problem. Generally, you can apply the equation s=vt to list the equations. However, the known number in the question and the required unknown number are all time, no distance, no speed, and cannot be represented by algebra. The relationship between the questions, and therefore must introduce auxiliary unknowns (ie parameters), so set every x