Answer:
The profit function is:
![P(x)=-x^2+1280x-3300](https://tex.z-dn.net/?f=P%28x%29%3D-x%5E2%2B1280x-3300)
The maximum value is 406, 300 occurring when x = 640.
Step-by-step explanation:
The revenue function is:
![R(x)=1300x-x^2](https://tex.z-dn.net/?f=R%28x%29%3D1300x-x%5E2)
And the cost function is:
![C(x)=3300+20x](https://tex.z-dn.net/?f=C%28x%29%3D3300%2B20x)
Then the total profit function will be:
![P(x)=R(x)-C(x)=(1300x-x^2)-(3300+20x)=-x^2+1280x-3300](https://tex.z-dn.net/?f=P%28x%29%3DR%28x%29-C%28x%29%3D%281300x-x%5E2%29-%283300%2B20x%29%3D-x%5E2%2B1280x-3300)
This is a quadratic function.
Therefore, the maximum value of the total profit will occur at its vertex point.
The vertex of a quadratic is given by:
![\displaystyle \Big(-\frac{b}{2a}, f\Big(-\frac{b}{2a}\Big)\Big)](https://tex.z-dn.net/?f=%5Cdisplaystyle%20%5CBig%28-%5Cfrac%7Bb%7D%7B2a%7D%2C%20f%5CBig%28-%5Cfrac%7Bb%7D%7B2a%7D%5CBig%29%5CBig%29)
In this case, a = -1, b = 1280, and c = -3300.
Then the point at which the maximum profit occurs is at:
![\displaystyle x=-\frac{1280}{2(-1)}=640](https://tex.z-dn.net/?f=%5Cdisplaystyle%20x%3D-%5Cfrac%7B1280%7D%7B2%28-1%29%7D%3D640)
And the maximum profit will be:
![P(640)=-(640)^2+1280(640)-3300=406300](https://tex.z-dn.net/?f=P%28640%29%3D-%28640%29%5E2%2B1280%28640%29-3300%3D406300)