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Math Help - Newtons Method

  1. #1
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    Newtons Method

    I need a little help solving this problem by using newtons method:

    Find x where y=6e^-x+6e^-2x+106e^-3x
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  2. #2
    Super Member Showcase_22's Avatar
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    Do we have to rearrange it to make x the subject or does y equal something?
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  3. #3
    Senior Member Spec's Avatar
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    I'm guessing it's y=f(x), so we use Newton-Raphson's method to find the root.

    x_{n+1}=x_n - \frac{f'(x_n)}{f(x_n)}

    Try using x_0 = 4
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  4. #4
    Senior Member Twig's Avatar
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    Quote Originally Posted by Spec View Post
    I'm guessing it's y=f(x), so we use Newton-Raphson's method to find the root.

    x_{n+1}=x_n - \frac{f'(x_n)}{f(x_n)}

    Try using x_0 = 4
    Actually its

     x_{n+1}=x_{n} - \frac{f(x_{n})}{f'(x_{n})}
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  5. #5
    Senior Member Spec's Avatar
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    Right, good catch.
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  6. #6
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    so apply that formula and im good?
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  7. #7
    Senior Member Twig's Avatar
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    You might have to do a few iterations to get close enough to the solution.
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  8. #8
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    Quote Originally Posted by Luck of the Irish View Post
    so apply that formula and im good?
    Yes, assuming that the problem is to solve the equation 6e^-x+6e^-2x+106e^-3x= 0. You never have said that.
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