1. The problem statement, all variables and given/known data Two cars approach an intersection at the same time. The red car is 300m east of the intersection and traveling at a speed of 60km/h. The blue car is 450m north of the intersection and traveling at a speed of 75km/h. When are the two cars the closest? 2. Relevant equations c^2 = a^2 + b^2 3. The attempt at a solution I converted the speeds into m/s first then used it in a pythagorean theorem equation and found the derivative. 75km/h = 20.8m/s 60km/h = 16.7m/s c^2 = (20.8t - 450)^2 + (16.7t - 300)^2 and when i do the derivative i get 20.2. But I was just wondering, does it make a difference whether i do 20.8t - 450 or 450 - 20.8t??