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  • Jun 25, 2007, 06:36 PM
    meggie_loo_2
    Pre Calculus
    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)
  • Jun 25, 2007, 11:38 PM
    Capuchin
    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.
  • Jun 26, 2007, 02:16 AM
    meggie_loo_2
    Quote:

    Originally Posted by Capuchin
    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!
  • Jun 26, 2007, 04:05 AM
    Capuchin
    A domain 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 it's all real numbers apart from 0 (beacuse 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:



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

    Let me know how you get on

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