１９４０年春，笔者就读于西北师范学院附中（抗日战争期间，北师大附中搬迁至陕西城固古路坝改名）高中三年级时，有一天，师院的一位毕业班同学到我们班上进行教学实习，讲虚数的运算．在课堂上有一位同学提出问题：“－２·－３＝？”试讲者当即回答：“－２·－３＝２... In the spring of 1940, when I was enrolled in the middle school of Northwest Normal University (the period of the Anti-Japanese War, when the Beijing Normal University Fuzhong was relocated to Shaanxi Chenggu Ancient Road Dam) in the third grade of high school, one day, a graduating classmate of the Normal College went to our class to perform Teaching practice, speaking imaginary operations. In class, one of my classmates asked a question: “-2·-3=?” The test taker immediately answered: “-2·-3=2...