Two car washes charge a basic fee plus a fee based on the number of extras that
are chosen. the table below shows the total costs for different car washes at
bubbles car wash. the total cost y (in dollars) for a car wash with x extras at
soapy car wash is represented by the equation y = x + 9. which car wash
charges more for the basic fee? how many extras must be chosen for the total
costs to be the same?

a. The first car wash charges more for the basic fee

b. 6 extras must be chosen for the total cost to be the same

Explanation:

The complete question is shown in the attached diagram

The general form of the linear equation is:

y = mx + c where m is the slope and c is the y-intercept

The y-intercept represents the initial value which, in the given problem, is the basic fee

For the first car wash, we are given the equation:

y₁ = x + 9

Now, we will start by getting the equation for the second car wash:

1- getting the slope:

The equation now is: y = 1.5x+c

2- getting the y-intercept:

To get the y-intercept, we will simply choose a point, substitute with it in the equation from 1 and solve for c. I will use point (2,9)

y = 1.5 x + c

9 = 1.5 (2) + c ............> c = 6

The equation for the second car wash is:

y₂ = 1.5x + 6

Part 1:

As mentioned above, the y-intercept represents the basic fee

For the first car wash:

y₁ = x + 9 ................> The basic fee is $9

For the second car wash:

y₂ = 1.5x + 6 ..............> The basic fee is $6

It is clear that the basic fee for the first car wash charges more for the basic fee

Part 2:

In both equations, x represents the number of extras. We want the total cost to be the same. So, we will simply equate y₁ and y₂ and solve for x

x + 9 = 1.5x + 6

1.5x - x = 9 - 6

0.5x = 3

x = 6

Let's verify:

For x = 6:

y₁ = x + 9 = 6 + 9 = $15

y₂ = 1.5x + 6 = 1.5(6) + 6 = $15

Total cost is the same. This means that 6 extras must be chosen for the total cost to be the same

Hope this helps :)

f(x) has value 150 at x= 0

and 0 at x= 3

so d(f(x))/dt = slope = -150/3 = -50