Given:
price p = $25
number of x units = -8p + 400
Find: solve for the value of x
Solution:
To determine the value of x, simply replace the variable "p" in the equation with 25.
![x=-8(25)+400](https://img.qammunity.org/2023/formulas/mathematics/college/cv3fusrb9hytjlwulu55rsojy7zejuxxxb.png)
Then, solve.
Multiply -8 and 25.
![x=-200+400](https://img.qammunity.org/2023/formulas/mathematics/college/f9utp916durrq2wqw04vt9zt0bd24353u5.png)
Add -200 and 400.
![x=200](https://img.qammunity.org/2023/formulas/mathematics/high-school/wu3h3vk4eqlqpqztzyqo0bkok4lawjuy5d.png)
Therefore, at $25, 200 units were sold.
Part F:
Since the equation of the revenue is R(x) = -8p² + 400p, then the graph must be a parabola opening down. Out of the 4 options, Only Options A and D show this.
However, upon comparing the two options, we see that the y-axis of the two graphs is different. Option A says that the y-axis is the price p while Option D says that the y-axis is the revenue R.
Since the given function is the revenue, then the y-axis should be R. The correct graph is Graph D.
Part G:
If the revenue is at least $4032, then let's replace the r(x) function with 4, 032.
![4,032=-8p^2+400p](https://img.qammunity.org/2023/formulas/mathematics/college/o0znur8aj44iczqknjoup8mgxda5v0t5za.png)
To solve for p, let's equate the function to zero by subtracting both sides of the function by 4, 032.
![\begin{gathered} 4,032-4032=-8p^2+400p-4032 \\ 0=-8p^2+400p-4032 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/mm9bjv9cb4aigu0ke9p3giiwrjp8kjap6s.png)
Then, let's solve for the value of "p" using the quadratic formula.
![p=(-b\pm√(b^2-4ac))/(2a)](https://img.qammunity.org/2023/formulas/mathematics/college/kbec5r84yuj9b99lpsqxzesfxnxs9xzph1.png)
Note that in the revenue function above, a = -8, b = 400, and c = -4032. Let's plug these values into the formula above.
![p=(-400\pm√(400^2-4(-8)(-4032)))/(2(-8))](https://img.qammunity.org/2023/formulas/mathematics/college/uosvwlkn27rqcc19sh4vzj0lsxoknafexy.png)
Then, simplify.
![p=(-400\pm√(160,000-129,024))/(-16)](https://img.qammunity.org/2023/formulas/mathematics/college/kl4jvt0oue4dv3p38rokyagjm5qvxabehf.png)
![p=(-400\pm√(30,976))/(-16)](https://img.qammunity.org/2023/formulas/mathematics/college/4szhwhvjuyiodqh3n1kagwb7w6d9nd9dt4.png)
![p=(-400\pm176)/(-16)](https://img.qammunity.org/2023/formulas/mathematics/college/j3xyhf2r3amorbcd9fqy8aw08iceayn5la.png)
Separate the plus and minus operations.
![p=(-400+176)/(-16)=(-224)/(-16)=14](https://img.qammunity.org/2023/formulas/mathematics/college/n1he8tos18jiqyhqh9x2jor8o5r7oco3qb.png)
![p=(-400-176)/(-16)=(-576)/(-16)=36](https://img.qammunity.org/2023/formulas/mathematics/college/suykdwyu37ezalbxb2q0a6pchmg8qn76p5.png)
The values of p are 14 and 36.
Hence, the company should charge a price between a minimum of $14 and a maximum of $36 to have a revenue of at least $4,032.