@@leaabdul-khalek5158 taking all possible situations into account meant that he needed to do point B and C and D, because it's possible to row in the middle. Towards the end is where we figured for points B and C. The only reason it seemed like we went directly for D is the fact that finding for D was more complicated than finding for B and C so it took longer to do. Also the fact that we did it first.
Go to 40:32 of the video. He explains that x has the the domain [0,8] and that you plug in values for A, D, and B to see which gives the smallest answer for time. However, if you set the derivative for total time = 0, you will solve for an x value that minimizes time to get from A to B. In other words, if x = 0, row directly to C and then run 8 km, etc...
on the 5th problem when taking the derivative of the inside function r^2-x^2, how did you end up with just -2x? do we not take the derivative of the r^2 as well since they are both inside the parentheses? (time stamp around 47:55)
