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动点问题是中考数学试题中备受青睐的常见题型,学生往往无从下手.此类题目因涉及分类讨论、转化化归、方程思想,综合性强,主要考查学生综合运用所学知识解决问题的能力和思维的灵活性,有一定的难度和探究性.笔者认为,只要抓住问题中的变与不变,让点、线动起来,从中找到规律,就能轻松获解,特别是当直线与圆、双曲线、抛物线相切时,可能取得最值,从而确定取值范围.现举几例说明.例1如图1,在平面直角坐标系xOy中,
The problem of moving point is a popular test for senior high school entrance examination questions, students often have no way to start .This topic involves classification discussion, conversion, equation thought, comprehensive, the main test students comprehensive use of the knowledge to solve the problem Ability and thinking flexibility, there is a certain degree of difficulty and exploration.In the author’s opinion, as long as the change in the problem to seize the same, let the lines move, find the law, you can easily get solution, especially when When the line is tangent to the circle, hyperbola, and parabola, it is possible to obtain the maximum value so as to determine the range of value. A few examples are given as follows: Example 1 As shown in Figure 1, in a Cartesian coordinate system xOy,