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Math Help - Polynomial or not

  1. #1
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    Polynomial or not

    y= (√x) + x^5 - 7x^6

    y= 3ix³ + 9


    My textbook says they are not polynomial functions. Why?

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  2. #2
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    "A polynomial is an expression of finite length constructed from variables and constants, using only the operations of addition, subtraction, multiplication, and non-negative, whole-number exponents" - Wikipedia

    Can you see what make them not a polynomial by using the description above?
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  3. #3
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    yeah, but both equations have positive whole integer exponents. I don't see how they aren't polynomial functions.

    My guess is the "√x" in the first equation and the "3ix³" in the second equation. If so, can someone explain why they make the equations not polynomial functions?

    Thanks.
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  4. #4
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    √x = x^(0.5)
    ("non-negative, whole-number exponents")
    This has a decimal exponent therefore it is not a polynomial.

    In the second one, 3ix³ has a imaginary number in it, therefore that part will not be graphed on the simple cartesian plane, leaving only the y=9 part to be graphed.
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