在讲授了正比例意义之后的一堂练习课上,我让学生举例说明成正比例关系的两种量,学生纷纷举手,我一连点了几个学生,他们都能准确地做出回答。这时,坐在最后一排的一位男同学还在坚持举手,我又请他回答。他说：“x-Y=0,x和Y成正比例。”多数学生听后都楞了一下。我问：“x-Y=0,x和Y成正比例,对吗?”学生几乎异口同声地回答：“不对!”我又问：“为什么不对?”他们又几乎是一齐说：“凡是加减关系的都不成正比例。”我 In an exercise class after teaching a proportionate sense, I asked the students to give examples of two things in direct proportion. Students raised their hands and I tried several students in succession, and they all responded accurately. At this time, sitting in the last row of a male classmate still insist on raising his hand, I asked him to answer. He said: “x-Y = 0, x and Y are proportional.” Most students are shocked after listening. I asked, “xY = 0, and x and y are proportional, right?” The students almost unanimously replied: “No!” I asked again: “Why not?” They are almost all together and said: “Any additions and subtractions Are not proportional. ”Me