I’m always a little disappointed in this because the answer is actually “they copied it from a textbook” rather than “they did some clever maths”. But I guess i

I’m always a little disappointed in this because the answer is actually “they copied it from a textbook” rather than “they did some clever maths”. But I guess it’s a triumph of knowing what solutions exist and when to use them, rather than brute forcing a solution (which is one of the reasons I still think non vocational computer science education is essential).