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Quick inverse question

  1. Jul 18, 2011 #1
    1. The problem statement, all variables and given/known data

    Inverse of g(x) = x/3 -5


    2. Relevant equations



    3. The attempt at a solution

    The inverse of the function

    g(x) = x/3 -5
    x= y/3 -5
    x +5 = y/ 3
    3x + 15 = y

    Is this correct?

    Or is it x+5 /3 ?
     
  2. jcsd
  3. Jul 18, 2011 #2
    Your original looks correct.

    If you have a graphic calculator, graph them both, the inverse should be a 90* rotation from the original, since you essentially have the same function with swapped axis.
     
  4. Jul 18, 2011 #3
    If you want to check to see if the inverse function you found is correct, all you need to do is form a composite function of the original function and its inverse. If the composite function of g(x) and g-1(x) is equal to x, then the inverse you found is correct.

    [itex]g[g^{-1}(x)]=(\frac{3x+15}{3})-5=(x+5)-5=x[/itex]

    Yes, the inverse you found is correct.
     
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