方程思想在初中数学中是应用最广泛的思维方法．在各类考试中常占５０％左右，一般是代数中形形色色的应用题，无不依赖于建立方程（组）来解决，这在前几讲中已获得充分展开．上一讲中其在几何方面的应用也见端倪，在这里让我们再看一些实例，以便深入理解这一好方法的精髓． The equation is the most widely used thinking method in junior high school mathematics. It often accounts for about 50% of all kinds of examinations, and it is generally applied to all kinds of problems in algebra, all relying on the establishment of equations (groups) to solve, which has been fully developed in the previous lectures. In the last lecture, its application in geometry was also seen. Here, let us look at some examples to further understand the essence of this good method.