几何最值问题因能综合考查特殊三角形、特殊四边形、圆、一次函数、二次函数以及轴对称、相似三角形等重要知识,具有较强的灵活性、创新性和挑战性,故一直备受全国各地中考命题者的青睐.不管题目怎样变化,此类问题最终常可用以下知识解决:(1)“垂线段最短”;(2)“两点之间线段最短”;(3)动点与定点最远(近)时距离最大(小);(4)动点与定直线最远(近)时距离最大(小);(5)一次函数、二次函数在某个范围内具有最大(小)值等.现举例 The most valuable problem of geometry is that it has a lot of important knowledge such as special triangle, special quadrilateral, circle, first-order function, quadratic function, axisymmetric, and similar triangle because of its flexibility, innovation and challenge. No matter how the subject changes, such problems can often be solved by the following knowledge: (1) “the shortest vertical line”; (2) “the shortest line segment between two points”; (3) (4) the distance between the moving point and the fixed line as far as possible (near) is the largest (small); (5) the first order function and the second order function are within a certain range With the largest (small) value, etc. Now for example