Answer:
(a)
[tex]f(x) = \left \{ {{5x;\ 0<x\le 5} \atop {5x-5; x > 5}} \right.[/tex]
(b) Rate = 5
(c) Rate = 5
Step-by-step explanation:
Given
The attached graph
Solving (a): The piece-wise function
For the first line
Calculate the slope of the first line
[tex]m = \frac{y_2 - y_1}{x_2 - x_1}[/tex]
Where
[tex](x_1,y_1) = (0,0)[/tex]
[tex](x_2,y_2) = (5,25)[/tex]
So, the slope is:
[tex]m = \frac{25 - 0}{5 - 0}[/tex]
[tex]m = \frac{25}{5}[/tex]
[tex]m = 5[/tex]
The equation is then calculated as:
[tex]y = m(x - x_1) + y_1[/tex]
Where: [tex]m = 5[/tex] and [tex](x_1,y_1) = (0,0)[/tex]
[tex]y = 5(x - 0) + 0[/tex]
[tex]y = 5(x) + 0[/tex]
[tex]y = 5x[/tex]
So, the function of the first line is:
[tex]f(x) = 5x;\ 0 < x \le 5[/tex]
For the second line
Calculate the slope of the second line
[tex]m = \frac{y_2 - y_1}{x_2 - x_1}[/tex]
Where
[tex](x_1,y_1) = (5,20)[/tex]
[tex](x_2,y_2) = (9,40)[/tex]
So, the slope is:
[tex]m = \frac{40 - 20}{9 - 5}[/tex]
[tex]m = \frac{20}{4}[/tex]
[tex]m = 5[/tex]
The equation is then calculated as:
[tex]y = m(x - x_1) + y_1[/tex]
Where: [tex]m = 5[/tex] and [tex](x_1,y_1) = (5,20)[/tex]
[tex]y = 5(x - 5) + 20[/tex]
[tex]y = 5x - 25 + 20[/tex]
[tex]y = 5x -5[/tex]
So, the function of the second line is:
[tex]f(x) = 5x -5;\ x>5[/tex]
Hence, the piece-wise function is:
[tex]f(x) = \left \{ {{5x;\ 0<x\le 5} \atop {5x-5; x > 5}} \right.[/tex]
Solving (b): The rate at which customers that buy up to 5lb buy.
[tex]x = 5[/tex]
This question implies that, we determine the rate at which this customer buys.
For [tex]x = 5[/tex]
[tex]f(x) = 5x;\ 0 < x \le 5[/tex]
The slope of the above function is 5.
So, this customer buys at the rate of $5 per lb
Solving (b): The rate at which customers that buy more than 5lb buy the extra pounds above 5lb.
For [tex]x > 5[/tex]
[tex]f(x) = 5x -5;\ x>5[/tex]
Assume x = 6
[tex]f(6) = 5 * 6 - 5[/tex]
[tex]f(6) = 30 - 5[/tex]
[tex]f(6) = 25[/tex]
Express as 20 + 5
[tex]f(6) = 20 + 5 * 1[/tex]
Assume x = 7
[tex]f(7) = 5 * 7 - 5[/tex]
[tex]f(7) = 35 - 5[/tex]
[tex]f(7) = 30[/tex]
[tex]f(7) = 20 + 10[/tex]
Express 10 as 5 * 2
[tex]f(7) = 20 + 5 * 2[/tex]
So, we have:
[tex]f(6) = 20 + 5 * 1[/tex]
[tex]f(7) = 20 + 5 * 2[/tex]
This can be generalized as:
[tex]f(x) = 20 + 5(x - 5)[/tex]
For the above functions;
20 represents the amount they buy the first 5
5 represents the rate at which they buy extra pounds above 5
Hence, they buy the extra pounds at the rate of $5 per pound
