Answer:
The minimum average cost is $643.75
It should be built 62.5 machines to achieve the minimum average cost
Step-by-step explanation:
The equation that represents the cost C to produce x DVD/BLU-ray players is C = 0.04x² - 5x + 800
To find the minimum cost differentiate C to equate it by 0 to find the average cost per machine and to find the value of the minimum cost
∵ C = 0.04x² - 5x + 800
- Differentiate C with respect to x
∴ 
∴ 
- Equate
by 0
∴ 0.08x - 5 = 0
- Add 5 to both sides
∴ 0.08x = 5
- Divide both sides by 0.08
∴ x = 62.5
That means the minimum average cost is at x = 62.5
Substitute the value of x in C to find the minimum average cost
∵ C = 0.04(62.5)² - 5(62.5) + 800
∴ C = 643.75
∵ C is the average cost
∴ The minimum average cost is $643.75
∵ x is the number of the machines
∴ It should be built 62.5 machines to achieve the minimum
average cost
X^2 + 10x + 11 = 0
x^2 + 10x = -11
x^2 + 10x + 25 = -11 + 25
(x + 5)^2 = 14 <===
x + 5 = (+-) sqrt 14
x = -5 (+-) 3.74
x = -5 + 3.74 = -1.26 <== solution
x = -5 - 3.74 = - 8.74 <== solution
SA = 2
+2

1. Find the radius.
R = 1/2D
6 x 1/2 = 3
R = 3
2. Plug them in.
SA 2(3.14)(3)(7) + 2(3.14)(3^2)
3. Solve
3 x 7 = 21
21 x 3.14 = 65.94
65.94 x 2 = 131. 88
3^2 = 9
9 x 3.14 = 28.26
28.26 x 2 = 56.52
4. Add them together.
131.88 + 56.52 = 188.4
Answer: 188.4 square millimeters