一次函数是初中数学的重要内容之一.同学们在利用一次甬数的有关知识解题时.会由于忽略限制条件、考虑问题不全面或思维定式的影响,而出现这样那样的错误.下面归类解析,供参考.一、忽略一次函数包括正比例函数例1若一次函数y=-3x+k的图象不经过第三象限,则k的取值范围是__.解:k≥0.【加分锦囊】容易忽略k=0的情况.正比例函数也是一次函数.二、忽略定义式中的限制条件k≠0 One-time function is one of the important contents of mathematics in junior high school.When students solve the problem by using the related knowledge of a number, it will be wrong because of neglecting the restriction conditions and considering the influence of incompleteness or thinking style. Class analysis, for reference. A neglected primary function includes a proportional function Example 1 If the image of a function y = -3x + k does not go through the third quadrant, then the range of k is __. Solution: k≥0. 【Extra points Tips】 Easy to ignore the case of k = 0. Proportional function is also a function of two, ignoring the constraints in the definition of k ≠ 0