Recent content by PITPin

Can you please tell me more about this equation? I have just started using derivatives in physics and I'm having trouble understanding where this equation came from and what it means. Is D a function? If so, I think the result would be 45.

Homework Statement Two cars leave at the same time (one from city A and the other from city B) and drive toward each other. They first meet d=45 km far from B . Both cars reach their destination (B for the former, A for the latter) and then start driving to their initial cities.The cars have...