A) Profit is the difference between revenue an cost. The profit per widget is
m(x) = p(x) - c(x)
m(x) = 60x -3x^2 -(1800 - 183x)
m(x) = -3x^2 +243x -1800
Then the profit function for the company will be the excess of this per-widget profit multiplied by the number of widgets over the fixed costs.
P(x) = x×m(x) -50,000
P(x) = -3x^3 +243x^2 -1800x -50000
b) The marginal profit function is the derivative of the profit function.
P'(x) = -9x^2 +486x -1800
c) P'(40) = -9(40 -4)(40 -50) = 3240
Yes, more widgets should be built. The positive marginal profit indicates that building another widget will increase profit.
d) P'(50) = -9(50 -4)(50 -50) = 0
No, more widgets should not be built. The zero marginal profit indicates there is no profit to be made by building more widgets.
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On the face of it, this problem seems fairly straightforward, and the above "step-by-step" seems to give fairly reasonable answers. However, if you look at the function p(x), you find the "best price per widget" is negatve for more than 20 widgets. Similarly, the "cost per widget" is negative for more than 9.8 widgets. Thus, the only reason there is any profit at all for any number of widgets is that the negative costs are more negative than the negative revenue. This does not begin to model any real application of these ideas. It is yet another instance of failed math curriculum material.
Answer: b and d
Step-by-step explanation:
Since the roots are x=2 and x=6, we can write the equation as

Substituting in the coordinates of the vertex,

So, the equation is
.
On expanding, we get 
Answer:
First, we know that the area of a rectangle of width W and length L is:
A = W*L
In the case of Roberto's plan, we can see that the length of the whole rectangle is:
L = 1.5ft + x + 1.5ft = 3 ft + x
And the width is:
W = 3ft + x + 3ft = 6ft + x
Then the area of the whole thing is:
A = (3ft + x)*(6ft + x)
This is what we wanted, a product of two polynomials that represents the area of Roberto's plot.
Now if we subtract the white square (is a square of sidelength x, then its area is A = x*x) we will get the area of the border;
The total area of Roberto's borders is:
Area of the border = (3ft + x)*(6ft + x) - x*x
= 3ft*6ft + 3ft*x + x*6ft + x^2 - x^2
= x*9ft + 18ft^2
There are 85 candy bars in each box, and he will have 340 candy bars left after he gives three boxes to a friend.