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Math Help - Bisection Method Help

  1. #1
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    Bisection Method Help

    Hi there,

    Im trying to find the real root of the equation 0.8x^3-4.2x^2+12.7=0. It is between -2(x0) and -1(x1). My problem is when i try to put the starting values(x0, x1) back into the equation to get y0 and y1 i get incorrect answers... I am easily able to do an equation such as x^5+2x^2-5=0, but not this... Can any body help me? is there something i should be doing with the decimal numbers multiplying x in the equation?
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  2. #2
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    Quote Originally Posted by nippy_nz View Post
    Hi there,

    Im trying to find the real root of the equation 0.8x^3-4.2x^2+12.7=0. It is between -2(x0) and -1(x1). My problem is when i try to put the starting values(x0, x1) back into the equation to get y0 and y1 i get incorrect answers... I am easily able to do an equation such as x^5+2x^2-5=0, but not this... Can any body help me? is there something i should be doing with the decimal numbers multiplying x in the equation?
    This question has nothing to do with Probability and Statistics. It will get moved to a more suitable subforum.
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  3. #3
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    Apologies, this is what i learn in maths with stats class is all. Where would it more suit? Calc?
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  4. #4
    Senior Member Twig's Avatar
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    Hi

    Im not sure I understand what you are asking.
    The real root?
    If youre looking for the roots to the polynomial this is solved with
    calculators or computers.
    And there are three real roots to this equation.
    I included a picture of the graph.
    Attached Thumbnails Attached Thumbnails Bisection Method Help-graph.jpg  
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  5. #5
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    Thanks anyway but as it happened ive learnt to use the newton raphson method aswell and this problem can easily be solved by newton raphson rather than bisection so ill just use that!
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