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一份中考数学试卷.往往知识覆盖面广,考查的知识点多,考试时间有限,如何在应试中取得良好的成绩?一方面必须有扎实的数学功底,另外必须注重解题策略,提高解题速度.一、运用逆向思维,简化解题过程例1计算(2x+3y)2-2(4x2-9y2)+(2x-3y)2.分析:若用完全平方公式展开,再去括号,合并同类项,运算量大,易出错,若能注意到完全平方公式的逆用,则原式=[(2x+3y)-(2x-3y)]2=(6y)2=36y2.
A math test in senior high school entrance examinations often covers a wide range of knowledge, examination of knowledge points, test time is limited, how to achieve good results in the exam? On the one hand must have a solid mathematical skills, in addition must focus on problem solving strategies, improve the speed of problem solving 1. Using Reverse Thinking to Simplify the Problem Solving Example 1 Calculate (2x+3y) 2-2 (4x2-9y2)+ (2x-3y) 2. Analysis: If you use the complete square formula to expand, go to the parentheses and merge the same class. The term is computationally intensive and error-prone. If you notice the inverse of the complete squared formula, the original formula = [(2x+3y)-(2x-3y)]2=(6y)2=36y2.