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一、两个教学问题为说明第1个教学问题,笔者摘录教科书(人教版7年级数学上册第34页)中的一段:怎样计算8÷(-4).根据除法是乘法的逆运算,就是求一个数,使它与-4相乘得8.因为(-2)×(-4)=8,所以8÷(-4)=-2.另一方面,我们有8×(-1/4)=-2.于是有8÷(-4)=8×(-1/4).对上述内容的教学,有教师提出:8÷(-4)转化为乘法得到8÷(-4)=-2,学生可以理解.但马上又转到:另一方面,我们有8×(-1/4)=-2,学
One or two teaching questions In order to illustrate the first teaching question, the author extracts a paragraph in the textbook (PEP 7th grade math book page 34): How to calculate 8 ÷ (-4). According to the division is the inverse of multiplication, Is to find a number that is multiplied by -4 to get 8. Since (-2) × (-4) = 8, 8 ÷ (-4) = - 2. On the other hand, we have 8 × (-1 / 4) = - 2. Then there is 8 ÷ (-4) = 8 × (-1/4). For the above teaching, some teachers proposed that 8 ÷ (-4) be converted to multiplication to get 8 ÷ (-4) ) = - 2, students can understand, but immediately turn to: on the other hand, we have 8 × (-1/4) = -2, learn