Question

Suppose it is found that a certain model of car sells y= -1.6(x-2)^2 + 4.8(x-2) + 16 cars per week, where x is the number of shops selling the car. Make a graph and estimate the best number of shops at which the car should be sold, from the point of view of the manufacturer.

Answer 1

Answer:

Approximately 4 shops would be the best number of shops which the car is sold, and the number of cars is 20.

Step-by-step explanation:

This is a quadratic function. Therefore, the first thing you need to do is assume some values for x, and then, calculate the value of y, (which would be the number of cars sold). In this way, you can do the graph.

Watch the following attachment, which is a document of excel, showing the graph and some values of x, that I assume

Now, even if you don't have the graph you can estimate the number of shops with the following expression of the summit:

X = -b / 2a

Where:

a: number that goes along with the x elevated.

b: number that goes along with the x, but without being elevated.

In this equation, the first thing we need to do, is rearrange it, that's because we have a (x-2) in the equation, and this could be really annoying.

First let's solve the (x-2)^2

(x-2)^2 = (x-2)(x-2) = x^2 - 2*2x + 2^2 = x^2 - 4x + 4

This is now multiplied by -1.6:

-1.6x^2 + 6.4x - 6.4

Now, multiply 4.8 by x-2:

4.8x - 9.6

Finally, let's arrange this:

-1.6x^2 + 6.4x - 6.4 + 4.8x - 9.6 + 16

-1.6x^2 + 11.2x - 6.4 - 9.6 + 16 = -1.6x^2 + 11.2x

This means that the graph do not have a "y" intercept, and the values of a and b are -1.6 and 11.2, therefore, we can estimate the best number of shops, calculating the summit of the graph (This is because s a quadratic function, and the graph is a parable, and the minimum or maximum point of the graph is reached in the summit)

Summit has X and Y values, the x value is (see formula above):

X = -11.2 / 2 * -1.6 = 3.5

and for the y value, just replace the X value in the equation:

Y = -1.6(3.5)^2 + 11.2(3.5) = -19.6 + 39.2 = 19.6

With this we can conclude that the best number of shops that sells this model of car, is 4 (rounded) and they all sell 20 cars (also rounded). See the graph below in the attachment.

Download xlsx

Answer 2

Answer:

The best number of shops at which the car should be sold is 3, from the point of view of the manufacturer.

Step-by-step explanation:

Below we can observe a graph of the function $y = -1.6(x-2)^2 + 4.8(x-2) + 16$. We have that for x = 3 (blue vertical line) and x = 4 (green vertical line) shops, the manufacturer sells the same number of cars per week y(3) = 19.2 and y(4) = 19.2, and this is the maximum number of car per week that can be sold. Because of operation costs (the less the number of shops, the cheaper the costs), the best number of shops at which the car should be sold from the point of view of the manufacturer is 3.