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View Full Version : Functions: graph f(x) = -3x^2, state domain, range

ELIZABETH J.
05-12-2006, 01:26 PM
The directions read: Graph each function, state the domain and the range.

The problem is: f(x)=-3x^2

The example on the other page says something about a formula : -b/2a what does that formula have to do with the problem, how do u use it.

Thank You :lol:

stapel
05-12-2006, 02:43 PM
The example on the other page says something about a formula : -b/2a what does that formula have to do with the problem
Look at the exercise. If the formula wasn't covered in class, it will at least have been explained in the example. What did the writer do with the value obtained? How was it displayed on the graph?

Eliz.

jacket81
05-12-2006, 03:21 PM
The domain is x is any real number.
Now, to find range, let y=-3x^2.
Now, divide by -3 on each side, giving you y/-3=x^2.
Now take squareroot of each side, giving you sq(y/-3)=x.
Now, y<=0, because y couldnt be greater then 0 since you couldnt have a squareroot of a negative number!
So range is <=0.

MatthewMM
05-12-2006, 08:17 PM
I'm also working on range and domain and it is quite confusing. I saw your previous example and I'm still confused, If I have y= 2x^2 +3 how would I get domain and range?

stapel
05-12-2006, 09:13 PM
If I have y= 2x^2 +3 how would I get domain and range?
Look at the graph.

Eliz.

MatthewMM
05-13-2006, 02:19 PM
I still do not know what I'm looking for. I looked up the definitions and it says that the range is the collection of all output values of a function and domain is the collection of all input values. That's Greek to me!

MatthewMM
05-13-2006, 02:49 PM
I have checked previous posts for the past 2 weeks and it seems that others have the same problem with domain and range. Could you give me a web site where I might be able to get more info on this so I can figure it out?

stapel
05-13-2006, 05:23 PM
Could you give me a web site where I might be able to get more info on this so I can figure it out?
Google returns about forty-three million results to a search for "domain range function". You might want to try looking through these results (http://www.google.com/search?hl=en&q=domain+range+function&btnG=Google+Search) for a lesson you find helpful.

Eliz.

ELIZABETH J.
05-17-2006, 12:20 PM
Thanks for your help, I kind of understand the problem a little better :D