a simple model for the cost of a car journey £C when a car is driven at a steady speed of v mph is?
c = 4500/v + v + 10
a) find value of v which minimises cost of the journey.
b) use d^2C/dv^2 to verify C is a minimum for this value of v
c) calculate minimum cost of the journey

answers:
Steve A say: c = 4500/v + v + 10
c' = 4500v^(2) +1
0 = 4500v^(2) +1
4500 = v^2
v = 30√5 = 67.08
c'' = 9000v^(3)
0 = 9000v^(3)
0 = v
c = £144.16

lbnzz say: ryafejxc

alex say: Hint:
a/
dc/dv=0
b/
d^2C/dv^2 >0

qobyb say: mrbsxtld
