>.< DOn't get this! (function question)

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How do you find the domain and range for an this equation:C(d) 120d + 100?

Also for the same equation here is a second question: During June and Septmeber, the company reduces the total cost of each housebaot rental by $40. Write the cost function for June and September.


If you need to origional statement, in case you can't figure what C or d is. Here it is: The cost in dollars, C(d), to rent a houseboat during July and August from a certain company is given by C(d) 120d+100, where d is the number of rental days.

THANKS A BUNCH!! ^_^
-ANNA
 
d=x (domain)
C(d)=y (range)

This is assuming that fractions of a day are possible (1/2 day, 1/4 day, etc.)

For these types of questions where it isn't purely mathematical, you have to apply some logic. First we can say that d>0 because you wouldn't pay $100 to rent a boat for 0 days (unless you like wasting money). :lol: Is there a max number of days that a boat can be rented? No, so the domain is d>0, or x>0.

When d=0, C(d)=100, so when d>0, C(d)>100. There's no max for the cost because there's no max for the number of days the boat can be rented. The range is C(d)>100, or y>100.

If the cost is decreased by $40 total, then C(d)=120d+100-40, or C(d)=120d+60
 
oh thanks, I get it now, cept how would you know it's the range thats > than 100? like, what if I thought that x>100, instead oy y >100. How would you know>???????????


-Anna

ps. ..I neer knew u lived at my mum's.. :roll:
 
Domain and range translate into "x values that are possible" and "y values that are possible" respectively.

x=days that a boat is rented
y=cost to rent a boat for x days

Explaination Of Domain
When you go to rent the boat, any number of days greater than 0 is possible, so x>0. "x" cannot equal 0 because, logically, no one would pay money to rent a boat for 0 days! :D

Explaination Of Range
How much you pay depends on how many days you rent a boat for. Pretend that a person rents a boat for 0 days, they would still have to pay $100. We already said though that a person renting a boat would always rent it for more than 0 days, so the cost will always be greater than $100, y>100.

I hope that clarifies it. :D
 
I have a quibble.
The function in part 1 applies only to July and August. Thirty days hath...
So 0<d<62
The function in part 2 applies only to June and September.
So 0<d<30
-------------------
Gene
 
Oh I didn't catch that. Gene is right, there should be maximums.

For the months of July and August only, it should be:

0<x ≤ 62
100<y ≤ 7540
 
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