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Math Help - Real zeros of a polynomial function

  1. #1
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    Real zeros of a polynomial function

    F(x) = 4x^3 + 7x^2 - 11x - 18
    The only one that I could find is -2...from what i have figured out...there is 1 positive real zero and 2 negative real zeros. I have tried everything i cant fins the other...could someone please help
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by aikenfan View Post
    F(x) = 4x^3 + 7x^2 - 11x - 18
    The only one that I could find is -2...from what i have figured out...there is 1 positive real zero and 2 negative real zeros.
    if you found one to be -2, you can do polynomial long division (or synthetic division) to find \left( 4x^3 + 7x^2 - 11x - 18 \right) \div (x + 2). the result will be a quadratic, and it is easy to find the roots of that
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    For the quadratic, I get 4x^2 - x - 9
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    for the zeros, I get -1.38
    as well as 1.63
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by aikenfan View Post
    For the quadratic, I get 4x^2 - x - 9
    yes, that is correct. now find the roots of that, there are two real roots

    Quote Originally Posted by aikenfan View Post
    for the zeros, I get -1.38
    as well as 1.63
    those seem about right. good job
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    Thank you for the help!
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