Julio César Martínez Romero 
A Differential Equation from a Parallel Universe 

Grade 9 was the most boring year of my life. I remember sitting in front of a map, trying to memorize the names and locations of all the eighty-five Mexican rivers. I sat there, fearing the exam where I would have to face an empty map of Mexico, and I would have to draw those rivers and write their names . . . and geography was the fun subject. Other subjects were terror stories. I did not understand a word of trigonometry. That subject was like watching an endless parade of odd names traveling on meaningless formulas. When the afternoon was warmest and we were all drowsy, our physics classes took place. We were fifty fourteen-year-old students in a smelly and suffocating classroom, watching a teacher copy a textbook on the blackboard, expecting us to copy it on our notebooks. This was my life when I was fourteen. If your life is not very different, then I wrote this book for you. Maybe you also find the mathematical exercises so absurd and boring that there is no way that you are going to spend your weekend studying for an exam. I used to be fourteen, and I was not very different from you. Then, I discovered algebra. I hope that after reading this book, your concept of mathematics might change too.

O autorze

I have been a mathematics teacher since 1985. I have taught students in their 5th and 6th grades of elementary education, in junior high school, in high school, and in bachelor and doctorate levels. I have been teaching Differential Equations at the Undergraduate Program on Genomic Sciences of the National University of Mexico since 2006.