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Thread: Evaluating Polynomial Function

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    Evaluating Polynomial Function

    The question is f(x2)=-x2+5x-2 So I plugged in the X2 as X and got -x4+5x2-2 but the multiple choice only has -4​4+x2-2, and if the multiple choice is correct what happened to the 5?
    Last edited by evking; 09-26-2017 at 12:10 PM.

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    What's the question?

    Quote Originally Posted by evking View Post
    The question is f(x2)=-x2+5x-2 So I plugged in the X2 as X and got -x4+5x2-2 but the multiple choice only has -4​4+x2-2, and if the multiple choice is correct what happened to the 5?
    It helps us if you give us the problem exactly as it was written when you got it.

    Was the question, "What is f(x)?" ?
    Was one choice, "-x + 5Sqrt[x] -2" ?
    "What happens in the event horizon, stays in the event horizon" -- Bob Brown (grandpa Bob)

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    Quote Originally Posted by Bob Brown MSEE View Post
    It helps us if you give us the problem exactly as it was written when you got it.

    Was the question, "What is f(x)?" ?
    Was one choice, "-x + 5Sqrt[x] -2" ?
    The question says " Polynomial Functions are shown below, plug in the following values as X to get the output values."
    I know for sure that -x4+x2-2 is the answer that is considered correct for that problem because it was graded as correct I am just curious why it is considered correct instead of -x4+5x​2-2. Hope that helps.

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    Quote Originally Posted by evking View Post
    The question says " Polynomial Functions are shown below, plug in the following values as X to get the output values."
    I know for sure that -x4+x2-2 is the answer that is considered correct for that problem because it was graded as correct I am just curious why it is considered correct instead of -x4+5x​2-2. Hope that helps.


    As a spin off from Bob Brown's post:
    Two things:
    (1) Is the original polynomial
    f(x) = -x2+5x-2
    so that, in reality,
    f(x2) = -x4+5x2-2

    (2) If that is the original polynomial 'printed in the book' it looks like maybe a typo and it should have been
    f(x) = -x2+x-2
    so that
    f(x2) = -x4+x2-2

    -Ishuda

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