# what are the failure cases of Newton Raphson Method? [duplicate]

I want list of failure cases for Newton-Raphson method. If possible please provide flow chart for Newton-Raphson method.

• Where the derivative is $0$ or undefined is an obvious case – Rhys Hughes May 15 '18 at 9:11
• Welcome to MSE. It will be more likely that you will get an answer if you show us that you made an effort. – José Carlos Santos May 15 '18 at 9:12
• i know few, i asked as it would be great if there will be a list of all possible failure cases at one place – abcdmath May 15 '18 at 9:29
• If the function is too fast-changing / "noisy" and our derivative estimate does not take this noise into account. – mathreadler May 15 '18 at 9:33
• With initial approximation $x_0$ to solution $x,$ if the derivative $f'$ of the function $f$ vanishes or takes values arbitrarily close to $0$ on the open interval between $x_0$ and $x$ then for some $n$ we may have $f'(x_n)=0$ for some $n$ or it may be that $f(x_n)\ne 0$ and that $f'(x_n)$ is so close to $0$ that $x_{n+1}$ can be "almost anywhere". – DanielWainfleet May 15 '18 at 13:23

$$x_{n+1}=x_n-\frac{f(x_n)}{f'(x_n)}$$
Since a fraction $\frac ab$ is undefined when $b=0$ or undefined, in this case that constiutes an equation $f(x)$ whose derivate cannot be found or is $0$.