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Math Help - function defined

  1. #1
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    Question function defined

    For the function defined by f(x)=5x-4, find a formula for f^-1(x). My answer is f^-1(x)= 1 divided by 5x-4, is this right. thanks for checking.
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  2. #2
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    f^{-1}(x) doesn't mean \frac{1}{f(x)}.

    Think of it this way:
    If y = f(x) = 5x-4 then the inverse function is denoted f^{-1}(x) and is just the expression with the x and y switched, and then solved for y.

    Switching y and x, you get:

    x = 5y - 4.

    Isolate the y to get:

    y = \frac{x+4}{5}

    So f^{-1}(x) = \frac{x+4}{5} = \frac{1}{5}x + \frac{4}{5}.
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  3. #3
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    Smile answer

    I see now where I was wrong. thanks for checking my answer.
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