Question

Bonnie buys a used car for $2500. She calculates her average monthly expenses for gas, insurance, and maintenance at $150 per month. The function f(x) = 150x + 2500 represents her total cost of owning the car for x number of months. What is the domain for this situation?

Answer 1

The domain is the "x" values. Realistically, for this specific problem, the domain has to be x >= 0 because we really cannot consider the time "before" her owning this car.

Answer 2

but, it wants to know when she bought the car, what is the domain after she bought the car. thats what it is asking.

Answer 3

That is not a problem. She bought the car at time = x = 0. And then she can have the car indefinitely (assuming perpetual life of the car), so we have x >= 0.

Answer 4

she bought the car at 2500 dollars, therefore she spent 2500 already, so obviously I get it now or I wouldnt be arguing this point.

Answer 5

It's like starting a job and getting paid. You start in some specific year that becomes the "base" year. We don't consider salary or wages for that job before being on that job.

And for this problem, if I understand you correctly, you just want to know the domain, which is the legitimate "x" valuies, and that is merely x >= 0.

Answer 6

and the equation they gave me is 150x+2500, whixh means its a constant 2500 no matter how many months she owns it.

Answer 7

Yes, that is true. 2500 is her sunk cost. She pays that and doesn't get that back. So, when she gets the car, and before she operates it, she is out a total of 2500. The next week, that will be a total of 2500 plus 1 times 150. The week after, 2500 plus 2 times 150 (150 for each week) and so on. It's the "and so on" that gives x >= 0.

Answer 8

-sighs dramatically- im gonna go with your answer but if I get it wrong, imma be mad!

Answer 9

before you go one thing.

Answer 10

yes?

Answer 11

To be really precise, if her expenses are looked at only once a week, you can say that this is a discrete function instead of a continuous function. Then you caould say that the domain is x = 0, 1, 2, 3, 4, ...

But I don't think your teacher is going to get that techinical.

Answer 12

its an online class so I'll now right after I turn it in if its right or not.

Answer 13

Then if your are asking for domain, the answer can only possibly be one of the two:

Either x >= 0

or

x = 0, 1, 2, 3, 4, ...

But I would think that your class would go with the first.

Answer 14

I just re-read your problem, and the fact that insurance is included, which is a continuous expense, it's the first one.

Answer 15

it was wrong :/

Answer 16

weird.....

Answer 17

You just want the domain? Are you sure that that is what the problem is asking for? Because that certainly is what the domain is.