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meggie_loo_2
Jun 25, 2007, 06:36 PM
I am having a lot of trouble with some summer pre-cal work I have to do. Can someone please help.

The directions are:
Find the domain and list in interval notation:
a) 3x+1

b) 3x+1
x^2-2x

c) sqrt(3x+1)

Please HELP!!

And other thats has really stumped me:
All its says is--

Expand (3+2y)^3

And one more:
Factor (8x^3-27)

Capuchin
Jun 25, 2007, 11:38 PM
Well, you'll need to tell us how far you have got with these, we will not give you the answers outright.

This one is fairly easy: Expand (3+2y)^3

Just write it out as (3+2y)(3+2y)(3+2y) and multiply it together in pieces. That's not even pre-calc.

meggie_loo_2
Jun 26, 2007, 02:16 AM
Well, you'll need to tell us how far you have got with these, we will not give you the answers outright.

This one is fairly easy: Expand (3+2y)^3

Just write it out as (3+2y)(3+2y)(3+2y) and multiply it together in pieces. That's not even pre-calc.

On the one you mentioned thats what I have but I wasnt sure what to do after putting (3+2y)(3+2y)(3+2y). So thank you.

And I havent really gotten anywhere on the domain ones. Maybe if you could explain to me what a domain is I might be able to get a little farther.

On the (8x^3-27) I dont know what to do because of the 8 in front of the x.
I know that if its x^3-27 you write x^3-3^3 then that equals (x-3)(x^2+3x+9).
Do you just write and 8 in front of the (x-3)??

But thanks again SO much!

Capuchin
Jun 26, 2007, 04:05 AM
A domain (http://en.wikipedia.org/wiki/Domain_%28mathematics%29) of a function of x is the set of possible values of x for which the function is defined.
For example, for your first question 3x+1, the domain is all real numbers. For \frac{1}{x} it's all real numbers apart from 0 (beacuse \frac{1}{0} is undefined). Now you do the others.

For (3+2y)(3+2y)(3+2y), you know how to do (3+2y)(3+2y) right? So do that first, and then multiply it by (3+2y) again.

For (8x^3-27) you can take the 8 out:

(8x^3-27)=8(x^3- \frac{27}{8})

Can you factorise it now? (I know you can!)

Let me know how you get on