本文介绍分类讨论思想在解一次函数问题中的应用,供参考.一、根据概念分类例1已知一次函数y=-3x+m不经过一象限,求m的取值范围.分析由于正比例函数是特殊的一次函数,故m分两种情况:1当m=0时,函数为正比例函数,因为k=-3<0,所以图象经过二、四象限,满足上述条件.2当m≠0时,k=-3<0,又函数图象不经过一象限,所以此函数图象经过二、三、 First, according to the concept of classification example 1 known function y = -3x + m does not go through a quadrant, find the range of m.As analysis of the positive proportional function Is a special one-time function, so m is divided into two cases: 1 When m = 0, the function is a positive proportional function, because k = -3 <0, so the image through the second and fourth quadrants to meet the above conditions. 0, k = -3 <0, the function image does not pass a quadrant, so this function image after two, three,