在初中阶段数学课程所学的多种函数中,二次函数的题型可谓最为灵活多变,它可融入的知识广而深,如三角形、四边形、相似、全等、最短路径、一次函数、最值等等,利用待定系数法求其函数解析式作为其重要的组成部分,对它的掌握显得尤为重要。待定系数法的四步口诀(一设、二代、三求、四写)相信很多同学都知道,但相较八年级下册所学习的一次函数,二次函数有着形态迥异的多种解析式,使得不少同学们在第一步设的环节举棋不定, Among the various functions learned in the maths curriculum of junior middle school, the questions of quadratic functions are the most flexible and varied, and they can be widely and deeply embedded in knowledge such as triangle, quadrilateral, similarity, congruent, shortest path, first order function, The most value and so on, the use of undetermined coefficient method to find its function analytic as an important part of its grasp is particularly important. I believe a lot of classmates know, but compared to the eighth grade of the first book to learn a function, the quadratic function has a variety of analytical forms of different forms , So many students in the first step set up indecisive,