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Math Help - Functions

  1. #1
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    Functions

    The function f is defined f:x = 1- 6x -3x^2
    1. evaluate ff(-2)

    2. Calculate the exact values of x which map onto themselves under the function f.

    ok i could do the first one(reletively simple) BUT the 2nd one i dont understand the question and cant do. CAN anyone explain what is meant by the 2nd question?????

    Also this to
    3. Determine the range of f
    4. Explain why f has and inverse.

    Question 2 ,3 and 4 i basically just dont understand can anyone explain them???
    Last edited by kingmaths; January 9th 2012 at 06:13 PM.
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  2. #2
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    skeeter's Avatar
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    Re: Functions

    The function f is defined f:x > 1- 6x -3x^2
    sorry, but I'm not familiar with the function notation you are using.

    From what you've posted, I see the inequality ...

    x > 1 - 6x - 3x^2

    ... is that what you meant?
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  3. #3
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    Re: Functions

    sorry
    F:x = 1- 6x -3x^2
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  4. #4
    Member kalyanram's Avatar
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    Re: Functions

    Hi KingMAths,

    This is what I think you mean

    f(x) = 1- 6x - 3x^2
    1. Was to find  f(f(-2)) (for which you have an answer already)

    2. Was to find all x such that f(x) = x
    so we have
    x = 1- 6x - 3x^2 \implies 1 - 7x -3x^2 = 0 \implies x = \frac{-7 \pm \sqrt{61}}{-6} by solving the quadratic.

    3. The range of f(x) thats simple enough if you write f(x) = 4 -3(x+1)^2 so the range is [4,-\infty) as x \in R

    Now the 4 question should be easy for you to solve.

    Kalyan
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