Can someone please help me with this?
I have no idea what's happening
http://imgur.com/Rqaxa4p
We know that at a speed of v km/h, the time taken (in hours) is T = 500/v (time = distance/speed).
Since we know the cost per hour as a function of v, c(v), the total cost is C = c(v)*T = (500/v)*c(v), where c(v) is the given cost function per hour.
So now we have C (total cost) as a function of v, so we can find the v to minimise C.