变换是数学中最常用、最重要的一种思想方法。通过各种变换,常常可以把复杂或未知转化为简单和已知,从而达到化归的目的。“‘变换’,亦称‘映射’、‘映象’、‘映照’、‘对应’等。设 A 与 B 是两个集,如果按照某个对应法,使 A 的每一个元素在 B 中有一个确定的元素与它对应,称这个对应法为从 A 到 B 的‘变换’。”(《辞海》,一九七九年版)初中数学没有也不可能介绍变换的这 Transformation is the most commonly used in math, the most important one way of thinking. Through various transformations, it is often possible to transform complex or unknown into simple and known, so as to achieve the goal of naturalization. 'Transform', also known as 'mapping', 'mapping', 'mapping', 'correspondence', etc. Let A and B be two sets, if according to some correspondence law, make each element of A in B There is a definite element corresponding to it, calling this correspondence law a 'transformation' from A to B. "(Cihai, 1979 edition) There is no impossibility in introducing math to junior high school mathematics