Tokyo-Moto Quad Racers found that its daily profit, P, in thousands, is given by P = -5x2 + 40x - 31 where x is the number of Quad Racers manufactured daily. Which of the following is the best estimate for the maximum profit the manufacturer can earn per day, in thousands?

Question

Tokyo-Moto Quad Racers found that its daily profit, P, in thousands, is given by P = -5x2 + 40x - 31  where x is the number of Quad Racers manufactured daily. Which of the following is the best estimate for the maximum profit the manufacturer can earn per day, in thousands?

imstuck · Answer

This is a parabola, an upside down one.  It has a max of y at a certain x.  That is what you are looking for.  In order to do this you will find the vertex of the parabola.  This is the point at x where y is the highest, aka the max profit.  Do you know how to do that?