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最常用的乘法公式有平方差公式:(a+b)(a-b)=a2-b2;完全平方公式:(a±b)2=a2±2ab+b2.在解题过程中,我们既要注意正向应用它们,又要注意逆向应用它们.1.正向应用,可把形如(a+b)(a-b)的代数式化为形如a2-b2的代数式,或把形如(a±b)2的代数式化为形如a2±2ab+b2的代数式,其特征是积化和差.2.逆向应用,可把形如a2-b2的代数式化为形如(a+b)(a-b)的代数式,或把形如a2±2ab+b2的代数式化为形如(a±b)2的代数式,其特征是和差化积.
The most commonly used multiplication formula is the square difference formula: (a+b)(ab)=a2-b2; the complete square formula: (a±b)2=a2±2ab+b2. We must pay attention to the problem solving process. Apply them positively, but also pay attention to the reverse application of them. 1. Positive application, can be algebraic form (a + b) (ab) into an algebraic form like a2-b2, or shape like (a ± b The algebraic formula of (2) is an algebraic formula of the form a2±2ab+b2, which is characterized by productization and difference. 2. The reverse application can convert algebraic forms such as a2-b2 to form (a+b)(ab). The algebraic formula, or algebraic form such as a2±2ab+b2, is an algebraic formula of (a±b)2, which is characterized by difference summation products.