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Math Help - Finding the Image of a point

  1. #1
    Senior Member sakonpure6's Avatar
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    Thumbs up Finding the Image of a point

    Hi i need help with the following question:

    The point(1,4) is on the graph of y= f(x). Determine the coordinates of the image of this point on the graph of y=3f[-4(x+1)]-2.


    What i tried was plunging in 4 for y and 1 for x and solving for the image but i did not get the correct answer which is (-5,10) from my book.

    Edit: what does it mean by "image" ?
    Last edited by sakonpure6; September 15th 2012 at 02:25 PM.
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  2. #2
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    Re: Finding the Image of a point

    sure it's not \left(-\frac{5}{4} , 10\right) ?
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  3. #3
    Senior Member sakonpure6's Avatar
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    Re: Finding the Image of a point

    can you tell me what you did and how you did it please! because this is what i got 4=3f(-8)-2 and im kind of stuck there
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  4. #4
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    Re: Finding the Image of a point

    "(1, 4) is on the graph of y= f(x)" means that f(1)= 4. In order to use "f(1)= 4", to calculate 3f(-4(x+1))- 2, we must have -4(x+1)= 1 which is the same as x= -5/4. And then, 3f(-4(x+1)- 2= 3f(1)- 2= 3(4)- 2= 10.
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  5. #5
    Senior Member sakonpure6's Avatar
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    Re: Finding the Image of a point

    Oh okay I understand now, thank you so much because I'm pretty sure this is going to be on my math test!
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