✔ 最佳答案
25.a. Cost of producing 100 rackets = C(100) = 2600 + 80(100) = $10 600
b.i. If n rackets were sold, then the total selling price = 250n
Hence, profit, P(n) = Selling price - cost = 250n - (2600 + 80n) = 170n - 2600
ii. I suppose the possible values of n are that P(n) >= 0
So, 170n - 2600 >= 0
n >= 2600 / 170 = 15.3
But as n has to be an integer, so n >= 16
iii. P(35) = 170(35) - 2600 = $3350
P(200) = 170(200) - 2600 = $31 400
30.a.i. Let's take a = 1, b = 2
f(1) + f(2) = (1)^2 + (2)^2 = 1 + 4 = 5
f(1 + 2) = f(3) = (3)^2 = 9, they are not equal
ii. Take f(x) = x^3
b.i. C(a + b) = pi(a + b) = pia + pib
C(a) + C(b) = pia + pib
They are equal
ii. Take P(x) = 4x, such that P(a + b) = P(a) + P(b)
This is known as the perimeter function of a square. By substituting a (positive) value of x (which is the length of a square), the value of the function gives the perimeter of the square. The property P(a + b) = P(a) + P(b) can be regarded as: the perimeter of a square with length (a + b) is equal to the sum of the perimeter of the squares with length a and b
參考: Prof. Physics