定义域、对应关系及值域是函数构成的三个要素．真申，定义域及时应关系是决定性因素．在指导学生解题时，我们总是习惯于从防错的角度出发提醒学生注意定出域，而较少引导学生面积极地发掘函数定义域的各种如能．为探索阎捷的解题途径取另．实际上，函数定义目的回用是多方面? Definition domain, correspondence and value domain are the three elements of function composition. Zhen Shen, definition domain and timely relationship are decisive factors. When instructing students to solve problems, we are always accustomed to remind students to set the domain from the perspective of mistake prevention, and less to guide students to actively explore the various functions of the domain of function. In order to explore Rui Jie’s solution to take another. In fact, there are many aspects of function definition and reuse.