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Math Help - Composite functions help

  1. #1
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    Composite functions help

    I have a few questions on composite functions:

    Consider 2 functions, f & g.
    1. Explain why the domains of f and g must be the same in order to +, - or x the functions.

    2. Explain why the domain of f is the range of g for f(g(x)).

    3. Let f = { (0,1) (1,3) (2,5) (3,7) } and g(x)=2x+1 ... Evaluate:
    a. (g ○ f )(0)
    b. (f ○ g)(2)
    c. (g ○ f)(3)

    Thank you!
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  2. #2
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    Oh come on will you not!
    These are such basic problems, why donít you post some kind of solutions?
    If you will not, the I must assume that you simply want someone to do you homework for you.

    I hope that will not happen!
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  3. #3
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    >_>

    Sorry, I'm aware I come across as a simpleminded person who just shows up the boards and asks for help, but at least I'm honest about it.

    The second question I don't get just because I do not know how to solve it with points and a function. I know how to solve it with JUST points or JUST functions.
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by finalfantasy View Post
    >_>

    Sorry, I'm aware I come across as a simpleminded person who just shows up the boards and asks for help, but at least I'm honest about it.
    what Plato is saying is that maybe you could tell us what you have been thinking about or what have you tried. we are aware that the problem might not be basic to you, and you shouldn't feel stupid if that's the case. we're not trying to be mean. on the contrary, it helps you more if you put some effort into it, and the only way we can know that you did that is if you show some of your work, or at least tell us what you were thinking about doing.

    The second question I don't get just because I do not know how to solve it with points and a function. I know how to solve it with JUST points or JUST functions.
    you mean the third question.

    just know that the domain is the set of all the first elements in the brackets and the range is the set of all the second elements in the brackets

    so for f(x), dom(f) = {0,1,2,3} and ran(f) = {1,3,5,7} so for instance, f(0) = 1. and remember, (g o f)(0) = g(f(0)). that's all the points are saying. now try the question and tell us of your progress.
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  5. #5
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    Oh man.

    You weren't right when you said it was a basic question.

    Looking over some sites and your advice actually helped.

    Nevermind, I got the answer for this. Not too sure how to word the first two though. But thanks everyone!
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  6. #6
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by finalfantasy View Post
    Oh man.

    You weren't right when you said it was a basic question.

    Looking over some sites and your advice actually helped.

    Nevermind, I got the answer for this. Not too sure how to word the first two though. But thanks everyone!
    tell us your ideas for the first two
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