二次函数是刻画现实世界中变量之间变化规律的一种常见的数学模型,是解决实际问题的一个重要工具,是初高中衔接的重要知识点,是初中数学的核心内容.在日常生活、生产和科研中,常常会遇到需要建立二次函数模型并综合运用一元二次方程、一次函数、不等式等知识和方法去解决的问题,此类问题也倍受中考命题者的青睐.二次函数建模问题一般放在中考试题的后三题,成为中考压轴题之一.由于实际问题中蕴含的条件及呈现方式各异,解决此类问题的关键是要认真观察、分析,抓住问题中的数 The quadratic function is a common mathematical model for describing the variation of variables in the real world and is an important tool for solving practical problems. It is an important knowledge point of convergence between junior and senior high schools and is the core content of mathematics in junior middle school.In daily life, Production and research, often encounter the need to establish a quadratic function model and the integrated use of quadratic equations, a function, inequality and other knowledge and methods to solve the problem, such issues are also much in charge of senior high school entrance examination candidates. Function modeling problems are generally placed on the latter three questions in the middle school entrance examination questions, becoming one of the axis problems in the test.As the actual problems contained in different conditions and presentation, the key to solving such problems is to carefully observe, analyze, grasp the problem In the number