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Math Help - Please help with inverse functions...

  1. #1
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    Please help with inverse functions...

    there are two functions:
    f(x)=(1/8)x-3    and   g(x)=x^3

    how do you find f^-1(g^-1(1))?
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by got_jane View Post
    there are two functions:
    f(x)=(1/8)x-3    and   g(x)=x^3

    how do you find f^-1(g^-1(1))?
    why don't you type with spaces?

    to find f^{-1}(x), start with
    y = \frac 18x - 3

    switch x and y and solve for y. that will give you f^{-1}(x). do a similar thing to find g^{-1}(x).

    can you continue?
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  3. #3
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    Quote Originally Posted by Jhevon View Post
    why don't you type with spaces?

    to find f^{-1}(x), start with
    y = \frac 18x - 3

    switch x and y and solve for y. that will give you f^{-1}(x). do a similar thing to find g^{-1}(x).

    can you continue?
    f^{-1}(x)=8x+3 and g^{-1}(x)=x^{1/3}
    and so f^{-1}(g^{-1}(1))=8(1)^{1/3}+3, I get 11 as an answer, but I checked the back of the book the correct answer is supposed to be 32...I wonder what I'm doing wrong.
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  4. #4
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by got_jane View Post
    f^{-1}(x)=8x+3 and g^{-1}(x)=x^{1/3}
    and so f^{-1}(g^{-1}(1))=8(1)^{1/3}+3, I get 11 as an answer, but I checked the back of the book the correct answer is supposed to be 32...I wonder what I'm doing wrong.
    your function for f^{-1}(x) is wrong. it is 8(x + 3) = 8x + 24
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  5. #5
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    Quote Originally Posted by Jhevon View Post
    your function for f^{-1}(x) is wrong. it is 8(x + 3) = 8x + 24
    oh! I got it! thank you so much! i appreciate it!
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