某日,几个备考高中入学考试的的初中学生来提问题,其中一个提问了一道流传甚广的题目的解法.为了讨论方便,现将此题转录如下:“在直线a一侧有两个定点A和B在直线a上确定一个点P,使得PA+PB的长最短.”问题一经提出,几个学生都面有难色,但却有一 One day, several junior high school students preparing for the entrance exam for high school come to ask questions, one of them asked a widely circulated solution to the problem. For the sake of discussion, this question is reproduced as follows: “There are two A fixed point A and B in the line a to determine a point P, PA + PB length of the shortest. ”Once the problem is presented, several students have a hard color, but there is a