quadratic
#quadratic
young grotto
vale drum
you can think of the equation as a quadratic graph, and so the minimum point is the vertex
its given in completed square form, so (b,c) will be the coords of the vertex
the y value is fuel needed in litres, so 10
and the x value is the velocity, so 80km/h
so b is 80km/h and c is 10l per 100km
v-b must equal to 0 for it to be the minimum, v is the x value, which is km/h
so b must also be km/h
if that makes sense
as b is affecting the x value
c is affecting the y value, and as the y value is litres per 100km, c must also be litres per 100km
yes
minimum value can only be 0 because any number squared is always positive
for part b keep the values of b and c the same and then substitute the new values given for y and v in
then rearrange for a
since in a graph only x (v here) and y values change and the rest in the equation of the graph is constant