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  1. #1
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    quadratics help

    f(x)=2x-7

    Find:

    I) f(3x+2)

    II) f^{-1}(x)
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  2. #2
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    Quote Originally Posted by william View Post
    f(x)=2x-7

    Find:

    I) f(3x+2)

    II) f^{-1}(x)
    i)  f(3x+2) = 2(3x+2)-7

    ii) Your function takes x, multiples it by 2, and subtracts 7. So the inverse will divide by 2 and add 7!

     f^{-1}(x) = \frac{x}{2} + 7
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  3. #3
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    Quote Originally Posted by Mush View Post
    i)  f(3x+2) = 2(3x+2)-7

    ii) Your function takes x, multiples it by 2, and subtracts 7. So the inverse will divide by 2 and add 7!

     f^{-1}(x) = \frac{x}{2} + 7
    Thank you very much sir. Will I) expand or is that the final result

    Quote Originally Posted by Mush View Post
    i)  f(3x+2) = 2(3x+2)-7

    ii) Your function takes x, multiples it by 2, and subtracts 7. So the inverse will divide by 2 and add 7!

     f^{-1}(x) = \frac{x}{2} + 7
    will I) go to

    f(3x+2)=6x+4-7

    f(3x+2)=6x-3

    ??
    Last edited by mr fantastic; February 22nd 2009 at 11:21 PM. Reason: Merged posts
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  4. #4
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    Quote Originally Posted by william View Post
    Thank you very much sir. Will I) expand or is that the final result



    will I) go to

    f(3x+2)=6x+4-7

    f(3x+2)=6x-3

    ??
    1. I don't know why you would use the word quadratics in the title of this thread since it is totally irrelevant to the question.

    2. Does the question ask you to expand? Does anyone expect you to expand? Has the question been answered if you don't expand? Capisce?
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  5. #5
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    Quote Originally Posted by Mush View Post
    i)  f(3x+2) = 2(3x+2)-7

    ii) Your function takes x, multiples it by 2, and subtracts 7. So the inverse will divide by 2 and add 7!

     f^{-1}(x) = \frac{x}{2} + 7
    I think the answer to the inverse will not be this. (second part of question).

    While taking inverse, first add 7 and then divide whole thing by 2.

    y = 2x - 7
    => y + 7 = 2x
    => x = (y + 7)/2


    So inverse function is  f^-1(x) = (x +7)/2
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