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有理数运算是中学数学中一切运算的基础,准确地理解有理数的运算法则、运算律,灵活运用一些运算技巧,可以提高运算的速度与准确性.下面举例说明,供同学们学习时参考.一、巧用运算律例1计算:(-18)+(6.5)+(+18)+(-6.5)+(3.5).分析:在有理数运算中,适当改变运算顺序,有时可以简化运算.本题利用加法的交换律、结合律把相反数结合在一起,可快速求得结果.解:原式=[(-18)+(+18)}+[(+6.5)+(-6.5)]+(3.5)=0+0+(+3.5)=3.5.
Rational number arithmetic is the basis of all computing in middle school mathematics, accurate understanding of rational number arithmetic, arithmetic law, flexible use of some computing skills, can improve the speed and accuracy of the operation. The following examples, for students to learn reference .A, (1): (18) + (6.5) + (+ 18) + (- 6.5) + (3.5) Analysis: In the rational number operation, the appropriate change in the order of operations, and sometimes can simplify the operation. Addition of the law of exchange, combined with the law of the opposite combination, can quickly find the result. Solution: Original = [(- 18) + (+18)} + [(+6.5) + (-6.5)] + ( 3.5) = 0 + 0 + (+ 3.5) = 3.5.