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Math Help - Inverse functions

  1. #1
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    Inverse functions

    find a formula for the inverse of the function:

    f(x) = (4x-1)/(2x+3)

    i substituted f(x) for x and tried solving, and i ended up with (3x+1)/2, but that doesnt check

    any help would be appreciated..
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  2. #2
    Eater of Worlds
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    Swap out your x and y

    x=\frac{4y-1}{2y+3}

    Now, divide so you can solve for y easier:

    \frac{4y-1}{2y+3}=2-\frac{7}{2y+3}

    Now, continue?.
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  3. #3
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by skabani View Post
    find a formula for the inverse of the function:

    f(x) = (4x-1)/(2x+3)

    i substituted f(x) for x and tried solving, and i ended up with (3x+1)/2, but that doesnt check

    any help would be appreciated..
    so you want to solve x = \frac {4y - 1}{2y + 3} for y

    \Rightarrow x(2y + 3) = 4y - 1 .........multiplied both sides by 2y + 3

    \Rightarrow 2xy + 3x = 4y - 1 ..........expanded the brackets on the left

    \Rightarrow 4y - 2xy = 3x + 1 ..........added 1 - 2xy on both sides

    \Rightarrow y(4 - 2x) = 3x + 1 .........factored out y from the left hand side

    \Rightarrow y = \frac {3x + 1}{4 - 2x}

    and that's your inverse function

    EDIT: Ah, I didn't see that you responded, galactus. But i'll leave what i did up since i used a different method
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