直线与曲线相交于不同两点的模型(简称为相交弦模型)是解析几何中一种常见的数学模型,特别在直线与圆锥曲线的位置关系的问题中,更为常见.而相交弦中涉及的最值问题,由于涉及的变量或参数过多,使得我们在面对含有多个参数的运算式子中,不能找准恰当的函数关系式,以致失去解决问题的信心.下面以两道例题为例,探讨如何巧设直线方程,找准函数关系式,进而解决相关弦中的最值问题. The intersection of a straight line and a curve at two different points (referred to as the intersectional chord model) is a common mathematical model in analytic geometry, and is more common in the problem of the positional relationship between straight lines and conic curves. The most value of the problem, because of the variables or parameters involved, so that we face in the formula with multiple parameters, can not find the right functional relationship, resulting in loss of confidence to solve the problem. The following two examples As an example, to explore how to skillfully set up a straight line equation, find out the functional relationship, and then solve the most value problem in the relevant string.