有理数的运算，若能合理、灵活地应用运算定律和其它技巧，常能避繁就简、化难为易．下面举例说明，供同学们学习时参考．例1计算下列各题：小结以上四题利用力。法交换律和结合律，都达到了简化计算的目的．其中①是把互为相反数的两个数对消；②是把分母相同或易于通分的分数 Rational arithmetic, if reasonable and flexible application of the laws of operation and other techniques, often avoid complications on the simple, difficult to change. The following examples illustrate the reference for students to learn. Example 1 Calculate the following questions: Summary The above four questions apply. The commutative law and the associative law have all achieved the purpose of simplifying the calculation. One of them is to cancel two numbers that are opposite to each other; 2 is to give the same or easier fraction of the denominator.