Given:
The amount of profit, y, made by the company, is related to the selling price of each widget, x, by the given equation
![y=-29x^2+1388x-10040](https://tex.z-dn.net/?f=y%3D-29x%5E2%2B1388x-10040)
To find:
The maximum amount of profit the company can make, to the nearest dollar.
Solution:
If a quadratic equation is
, then the vertex is
![Vertex=\left(-\dfrac{b}{2a},f(-\dfrac{b}{2a})\right)](https://tex.z-dn.net/?f=Vertex%3D%5Cleft%28-%5Cdfrac%7Bb%7D%7B2a%7D%2Cf%28-%5Cdfrac%7Bb%7D%7B2a%7D%29%5Cright%29)
If a>0, then vertex is the minimum point and if a<0, then the vertex is the maximum point.
We have,
![y=-29x^2+1388x-10040](https://tex.z-dn.net/?f=y%3D-29x%5E2%2B1388x-10040)
Here,
. Clearly, a<0. So, the vertex is the point of maxima.
![-\dfrac{b}{2a}=-\dfrac{1388}{2(-29)}](https://tex.z-dn.net/?f=-%5Cdfrac%7Bb%7D%7B2a%7D%3D-%5Cdfrac%7B1388%7D%7B2%28-29%29%7D)
![-\dfrac{b}{2a}=-\dfrac{1388}{-58}](https://tex.z-dn.net/?f=-%5Cdfrac%7Bb%7D%7B2a%7D%3D-%5Cdfrac%7B1388%7D%7B-58%7D)
![-\dfrac{b}{2a}\approx 23.931](https://tex.z-dn.net/?f=-%5Cdfrac%7Bb%7D%7B2a%7D%5Capprox%2023.931)
Putting x=23.931 in the given equation, we get
![y=-29(23.931)^2+1388(23.931)-10040](https://tex.z-dn.net/?f=y%3D-29%2823.931%29%5E2%2B1388%2823.931%29-10040)
![y=-16608.09+33216.228-10040](https://tex.z-dn.net/?f=y%3D-16608.09%2B33216.228-10040)
![y=6568.138](https://tex.z-dn.net/?f=y%3D6568.138)
The vertex is at (23.931,6568.138).
Therefore, the maximum profit is $6568.138 when x=23.931.