At travel speed "x" (constant velocity in mph), there are "y" accidents at nighttime for every 100 million miles of travel where y is given by y=-6.1x^2+752x+22620. At what travel speed does the greatest number of accidents per 100 million miles traveled occur?

Question

phi · Answer

y=-6.1x^2+752x+22620.

this is the equation of a parabola with the shape $ \cap $
it has a peak at the vertex when 
$$ x = \frac{-b}{2a} $$
where a,b, and c are 
$$ y = a x^2 +bx +c $$
match that general from with your parabola to find a and b
then find the x value of the vertex.