Why does minus and minus make plus? | Hee Oh - Advice to young mathematicians - Abel Prize 2026

Why does minus minus make plus? Hee Oh couldn't understand it as a child. We therefore invite you to share your best explanation in the comments. Professor Hee Oh talks about how she went from disliking mathematics so much that it gave her stomach aches to becoming the first woman to hold a tenured professorship in mathematics ‪@yale‬⁩. As a child she was convinced she had found counterexamples to the triangle inequality using matchsticks and pencil drawings, and she lost 40 points on a single test because of double negatives. Everyone else seemed to find it obvious; she concluded she was simply bad at math, and a doctor confirmed there was nothing wrong with her except that she didn't like the subject. Everything changed when she learned what a proof is, and again in her first calculus class at Seoul National University, when Professor Hong-Jong Kim wrote on the blackboard: "Mathematics is beautiful." A PhD student of Abel laureate Gregory Margulis and a member of the Abel Committee, she describes her career of almost 40 years as a journey to understand what he meant. Her most important advice to young mathematicians: make friends with a problem: Spend time with it, try to understand it, and be patient. Key Takeaways: Not obvious isn't the same as not able: Struggling with what others find self-evident can be a sign of asking deeper questions, not of lacking talent. Rigor brings clarity: Confusion often dissolves once you understand the precise definitions – her "counterexamples" failed because mathematical lines have no thickness. Make friends with the problem: Spend time with it, see it from its perspective and approach it with humility – it helps psychologically when you're stuck. Curiosity is the engine: Like a reader of a murder mystery, wanting to know what happens is what keeps you at the desk long after midnight. Have confidence and courage: Don't be intimidated by people who seem smarter – deep and difficult problems take time, and you have to believe you can get there. 00:00 Introduction 00:36 "I did not like math at all" 00:49 Two "counterexamples" to the triangle inequality 02:09 Why does minus minus make plus? 03:08 Stomach aches and a doctor's verdict 03:29 What was wrong with the counterexamples 04:10 Her answer to minus minus: groups 04:49 "Mathematics is beautiful" 06:54 Advice: make friends with the problem 07:17 Curiosity as a driving force 09:40 Advice to her 15-year-old self #AbelPrize #Mathematics #careeradvice #STEM