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学习了有理数的乘除法后,老师像往常一样,让同学们先分小组讨论有理数的乘除运算的技巧,然后,请各组派一名代表到讲台上讲解本组所总结的方法和技巧.下面摘取几个片段,与同学们分享.学生小亮:多数相乘,先定符号例1计算:(-2.5)×2/3×(-6)×(-4).分析:题目中有三个负因数,故结果的符号应为负.解:原式=-(2.5×2/3×6×4)=-40.点评:几个非零有理数相乘,结果的符号由负因数的个数决定.学生小波:遇除化乘,统一进行例2计算:-101/8÷9/4×4/3÷(-2).分析:可根据除以一个数等于乘以这个数的倒数,将除法运算转化为乘法运算.
After learning the multiplicative division of rational numbers, the teacher, as usual, asked the students to divide their groups into rational numbers for multiplication and division, and then ask each group to send a representative to the podium explaining the methods and techniques summarized in this section. Take a few fragments, share with classmates. Students small light: Most multiply, first set the symbol Example 1: (- 2.5) × 2/3 × (-6) × (-4). Analysis: There are three The result sign should be negative. Solution: Original = - (2.5 × 2/3 × 6 × 4) = - 40. Comments: The multiplication of several non-zero rational numbers results in the sign of the negative factor The number of decisions. Student Wavelet: Case of abatement multiplication, unified Example 2 Calculation: -101 / 8 ÷ 9/4 × 4/3 ÷ (-2). Analysis: According to the division by a number is equal to the number of times Countdown, the division operation into multiplication.