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Math Help - graphing question

  1. #1
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    graphing question

    for the longest while i've been working on this question
    can any 1 help me out here

    Code:
     
    f(x) = 3^(x + 1) and g(x) = 3-x + 3 .
    Find the point of intersection of the graphs of f and g by solving f(x) = g(x).
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  2. #2
    MHF Contributor Unknown008's Avatar
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    3^{x+1} = 3-x+3

    Is that it? g(x) seems strange...
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  3. #3
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    sorry this is what the question said
    Code:
    3^{x+1} = 3^{-x+3}
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  4. #4
    MHF Contributor Unknown008's Avatar
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    3^{x+1} = 3^{3-x}

    Insert log on both sides:

    \log 3^{x+1} = \log 3^{3-x}

    (x+1)\log 3 = (3-x)\log 3

    (x+1) = (3-x)

    Can you finish now?
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  5. #5
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    so am i solving for x
    using quadratic

    then what
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  6. #6
    MHF Contributor Unknown008's Avatar
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    You don't need to use quadratic...
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  7. #7
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    so how am i going to get the points
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  8. #8
    MHF Contributor Unknown008's Avatar
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    You solve for x...

    x+1 = 3-x
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  9. #9
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    3-x -x -1=0

    -2x +2 = 0
    x = -1


    is it this
    what do i do after
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  10. #10
    MHF Contributor Unknown008's Avatar
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    Since you are looking for the point of intersection, you are looking for a coordinate.

    You already have the x coordinate, what can you do it this and the two equations:

    f(x) =3^{x+1}

    g(x) = 3^{x-3}
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  11. #11
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    so i solved the equation above and got -1
    so am i going to substitute it in fx and gx
    and solve
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  12. #12
    MHF Contributor Unknown008's Avatar
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    Yes

    Substituting in either f(x) or g(x) should be enough though.
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  13. #13
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    i guess i have to substitute for both

    bcuz they said for f and g

    for f i got (-1,1)
    any suggestions
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  14. #14
    MHF Contributor Unknown008's Avatar
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    Well... actually you didn't solve for x properly... I thought that you were doing the calculations well, but a small mistake crept in:

    -2x +2 = 0

    -2x = -2
    x = 1

    Now, find your y coordinates.
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  15. #15
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    cud u jus verify this for me
    0 = 3-1-2x
    0 = 2-2x
    -2= -2x
    x=1



    f(x) = 3^(x+1)

    f(x) = 3^ (1+1)
    f(x)= 9


    g(x) = 3^(-1+3)

    g(x) = 3^(2)
    g(x) = 9
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