北师大版数学九年级上册第一章《证明(二)》中,出现了线段和差的证明问题,此后多次出现。从“求证一条线段等于其它线段的和差”问题的本质来看,大部分可以认为是“证明线段相等问题”的变形和发展。也有一些线段和差问题,较难 Beijing Normal University edition of mathematics ninth grade on the first chapter “proof (b)”, there has been a proof of line and poor, then many times. From the point of view of the “proof of a line segment equal to the sum of the difference of other lines”, most of it can be considered as the deformation and development of “proof of equality of line segments.” There are also some lines and poor problems, more difficult