一、揭示实质尽管乘法公式灵活多变 ,但无论怎么变也无外乎是在系数、指数、项数、符号上作变化 ,如果学生能抓住问题的实质 ,就不会混淆、误用公式。所谓揭示实质 ,就是记公式时不从形式上记 ,如公式 (a+b) (a- b) =a2 - b2 ,要会用语言准确地描述 ,即第一项与第二项的和乘以 First, revealing the essence Although the multiplication formula is flexible, no matter how it is changed, it is nothing more than a change in coefficient, index, item number and symbol. If students can grasp the essence of the problem, they will not confuse or misuse the formula. . The so-called revealing essence is that when the formula is written, it is not recorded formally. For example, the formula (a+b) (a-b) = a2 - b2 should be accurately described in language, that is, the sum of the first and second terms. To