Question 548898
N(x)=-0.5x^2+15x+12

this is an inverted parabola since coefficient of x^2 is negative

x coordinate of vertex = -b/2a
b=15, a=-0.5

-b/2a= -15/2(-0.5)= -15/-1 = 15

so sales will peak on the 15th day.

plug value of x in the equation to get the y coordinate of the vertex

((-0.5) * (15^2)) + (15 * 15) + 12 = 124.5
maximum sales will be 124 on the 15th day