Finding the roots through Newtons method

In summary, the conversation is about using Newton's method to approximate the zeros of a function. There is a question about how many iterations should be done and whether certain conditions need to be applied. It is suggested to stop iterating when the difference between two successive approximations is less than 0.001.
  • #1
Telemachus
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Homework Statement


In each of the following items approximate the zeros of [tex]f[/tex] using Newton's method. Continue iterating until making two successive approximations differ at most in 0.001.

The Newton iteration: [tex]x_{n+1}=x_n-\displaystyle\frac{f(x_n)}{f'(x_n)}[/tex]

Well, I have a doubt about this. I'm not sure if it's asking me to iterate till [tex]|x_{n+1}-x_n|\leq{0.001}|[/tex], or if I should apply some of this:

[tex]k_1>0[/tex], [tex]|f'(x)|\geq{k_1}[/tex] and [tex]|f''(x)|\leq{}k_2[/tex] for all [tex]x\in{}[/tex], then:

[tex]|x_{n+1}-r|<\displaystyle\frac{k_2}{2k_1}|x_n-r|^2[/tex]

If [tex]r\in{}[r-\delta,r+\delta]\subset{[a,b]}[/tex], and [tex]\delta<2(\displaystyle\frac{k_1}{k_2})[/tex]

[tex]|x_{n+1}-r|<\displaystyle\frac{2k_1}{k_2}(\displaystyle\frac{\delta}{\displaystyle\frac{2k_1}{k_2}})^2n[/tex]
 
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  • #2
Stop when [tex]|x_{n+1} - x_n| < 0.001[/tex].
 

1. How does Newton's method work?

Newton's method is an iterative algorithm used to find the roots of a function. It involves selecting an initial guess for the root and using the derivative of the function to refine the guess in each iteration until the desired level of accuracy is achieved.

2. What is the advantage of using Newton's method?

Newton's method is known for its rapid convergence, meaning it can find the root with a high level of accuracy in a small number of iterations. This makes it a popular choice for finding roots in complex functions.

3. Can Newton's method find all types of roots?

Newton's method is most suitable for finding real roots of continuous functions. It may not work for discontinuous functions or functions with multiple roots that are close together.

4. How do you know when to stop iterating in Newton's method?

The iteration in Newton's method should continue until the difference between two consecutive approximations of the root becomes smaller than a predefined tolerance level, indicating that the desired level of accuracy has been achieved.

5. Are there any limitations to using Newton's method?

Newton's method may fail to converge if the initial guess is not close enough to the root or if the function has a complex or non-smooth behavior near the root. It also requires knowledge of the derivative of the function, which may be difficult to obtain in some cases.

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