The point of departure in this study is that differences in solving second-degree equations result from differences in what is presented to the students in a learning situation. However, the specified aim is to describe what kind of differences seem to be crucial for learning, and what does seem fruitless. The study is carried out in an upper secondary school in Sweden. Data consist of video-recorded lessons and tests. Two teachers and 45 students participated in this study. The analysis has been made with the aid of variation theory. The results show that the teachers focused on different aspects of a second-degree equation, and that this implied different learning outcomes as some of the aspects were not critical to promoting learning while others were. (Contains 3 tables and 4 figures.)