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 underst...