论文部分内容阅读
大家知道,初中数学常见的最值问题都是利用“两点之间,线段最短”、“垂线段最短”和建立二次函数后求,但有些问题不能直接求,需要有一个转换,才能解决问题.例1(2015年济宁)如图1,⊙E的圆心E(3,0),半径为5,⊙E与y轴相交于A、B两点,(点A在点B的上方),与x轴的正半轴相交于点C,直线l的解析式为y=3/4x+4,与x轴相交于点D,以C为顶点的4抛物线经过点B,(1)求抛物线的解析式;(2)判断直线l与⊙E的位置关系,并说明理由;
We all know that the most common problems in junior high school mathematics are the use of “between the two points, the shortest line segment ”, “vertical line segment ” and the establishment of quadratic function after seeking, but some problems can not be directly seeking, you need to have a Example 1 (Jining in 2015) As shown in Figure 1, the center E (3,0) of circle ⊙E has a radius of 5, and ⊙E intersects the y axis at points A and B. (Point A is at point B), intersects the positive semi-axis of the x-axis at point C, the resolution of the straight line l is y = 3 / 4x + 4, intersects the x-axis at point D, (1) to find parabolic analytical expression; (2) to determine the linear relationship between l and ⊙ E, and explain the reasons;