对于刚进入初中七年级的学生来讲,一元一次方程模型的建立过程中未知数设法至关重要。我发现不少学生在设未知数这一环节存在一些困惑,为了帮助学生解决这个困惑,特总结设未知数支招例析。诚然,建立方程模型的前提是:(1)认真研读题目。(2)理解题意。现支招例析如下:支招一:直接设未知数法什么是直接设未知数法呢?简单地说,就是问什么,设什么。例1.某工厂去年的生产总值是545万元,比5年前的10倍还多18万元,那么5年前这个工厂的年产值是多少万元?解:设5年前这个工厂的年产值是x万元,根据题意,得 For students just entering the seventh grade of junior high school, unknowns in the process of establishing a one-equation model are of crucial importance. I found a lot of students in this part of the unknown there are some confusion, in order to help students solve this puzzled, special summary set unknown tool analysis. Admittedly, the premise of establishing the equation model is: (1) to study the subject seriously. (2) Understand the questions. Current Weaponry analysis is as follows: Weapon 1: directly set the unknown law What is directly set the unknown law? Simply put, is what to ask, what to set up. Example 1. A factory last year’s GDP was 5.45 million yuan, more than 10 times five years ago, 180,000 yuan, then 5 years ago, the annual output of this plant is how many million? Solution: Set 5 years ago this factory The annual output is x million, according to the title, too