探求极值问题是初中数学的一种常见的题型,特别是近年的中考题、数学竞赛试题.面对具体的极值问题,需根据题设的条件和结构特点,灵活选取恰当的方法.本文介绍如何用几何知识求一类极值问题,供同学们参考. Exploring the extremum problem is a common type of mathematics in junior high school mathematics, especially in recent years, the middle exam questions, mathematics contest questions. In the face of specific extremum problems, we need to flexibly select the appropriate method according to the conditions and structural characteristics of the title. This article describes how to use geometry knowledge to find a class of extremum problems for students to refer to.