众所周知,“三角形任意两边之和大于第三边,任意两边之差小于第三边”.解题中前者用的较多,后者应用较少.纵观整个初中几何,凡是涉及两线段之差的题目几乎都与三角形任意两边之差小于第三边有关.中考试题中,有时会出现求两线段之差最大值的题目,但不少学生对此类题目感到很棘手,本文拟就这类题型作一初步分析,希望对学生有所帮助. As we all know, “triangle on both sides of the sum is greater than the third side, the difference between any two sides is less than the third side.” The former used more problems, the latter less used .Above all the junior high school geometry, Almost all of the problems with the triangle on both sides of the difference is less than the third side of the middle of the examination questions, sometimes appear to ask the maximum difference between the two lines of the title, but many students feel very difficult for such topics, Such questions for a preliminary analysis, hoping to help students.