A) Demand function
price (x) demand (D(x))
4 540
3.50 810
D - 540 810 - 540
----------- = -----------------
x - 4 3.50 - 4
D - 540
----------- = - 540
x - 4
D - 540 = - 540(x - 4)
D = -540x + 2160 + 540
D = 2700 - 540x
D(x) = 2700 - 540x
Revenue function, R(x)
R(x) = price * demand = x * D(x)
R(x) = x* (2700 - 540x) = 2700x - 540x^2
b) Profit, P(x)
profit = revenue - cost
P(x) = R(x) - 30
P(x) = [2700x - 540x^2] - 30
P(x) = 2700x - 540x^2 - 30
Largest possible profit => vertex of the parabola
vertex of 2700x - 540x^2 - 30
When you calculate the vertex you find x = 5 /2
=> P(x) = 3345
Answer: you should charge a log-on fee of $2.5 to have the largest profit, which is $3345.
The answers for one, two, and three are:
False
True
True
The awnser would be -11. A minus and a minus creates a plus so it adds up to -11
The best way to approach this problem is to find out how much fell in week. As you know what two weeks is, you simply have to halve this, giving you that one week is 5 inches of rain. One you have this, you can multiply this by 4 (as this will give you 4 weeks, or 28 days), and this gives you 20 inches in 28 days. You should then find the odd three days. If you divide 5 by 7, this will give you the rain fall in one day. 5/7= 0.8 inches per day. You then have top multiply this by 3 (as you've got three odd days), and this gives you 2.4. You then have to add together 2.4 and 20, giving you 22.4
Therefore, if the rain continued to fall at the same rate for 31 days, it would receive 22.4 inches of rain.
Hope this helps :)
