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  1. #1
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    Help on this quadratic problem

    Let f(x) = x^2 - 2x. Let e be a real between -1< e < 15. Find a c where 1 < c < 5 such that f(c) = e.

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    Last edited by CaptainBlack; November 4th 2010 at 02:36 PM.
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  2. #2
    MHF Contributor Also sprach Zarathustra's Avatar
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    Quote Originally Posted by storchfire1X View Post
    Let f(x) = x^2 - 2x. Let e be a real between -1< e < 15. Find a c where 1 < c < 5 such that f(c) = e.

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    C=2
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  3. #3
    MHF Contributor Also sprach Zarathustra's Avatar
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    Double post. Sorry.
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  4. #4
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    It seems to me that 1,5) \to (-1,15)" alt="f1,5) \to (-1,15)" />
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  5. #5
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    Perhaps the original post has been changed but I don't see how either of those really helps. If c= 2, then f(c)= f(2)= 4- 4= 0 but the problem said "let e be any number between -1 and 15 and find c such that f(c)= e". Yes, f maps (1, 5) to (-1, 15) which means there is a solution.

    storchfire1X, the equation f(x)= x^2- 2x= e is the same as the quadratic equation x^2- 2x- e= 0. You can use the quadratic formula to solve it. The quadratic formula will give two roots for the equation but only one of them will be between 1 and 5
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