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Math Help - Functions

  1. #1
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    Functions

    f(x) = 3x-2
    if f(a)=4 determine the numerical value of f-1(4)
    I'm really clueless on how to do this one.
    I started with:
    4 = 3x-2
    x = 2

    and then tried substituting that into the inverse which is y = (x+2)/3
    to get: 2+2/3 = 4/3 = 1.333....
    could anyone tell me if I did this correctly?
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by xxlvh View Post
    f(x) = 3x-2
    if f(a)=4 determine the numerical value of f-1(4)
    I'm really clueless on how to do this one.
    I started with:
    4 = 3x-2
    x = 2

    and then tried substituting that into the inverse which is y = (x+2)/3
    to get: 2+2/3 = 4/3 = 1.333....

    could anyone tell me if I did this correctly?
    the last part is off. you're working so hard, you already passed your stop. you simply have to find the "a", which you did. it's 2

    remember, if f(a) = 4 we would have f^{-1}(4) = a by taking the inverse function of both sides of the equation.
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