An equation f(x) = 0 has two roots in the interval between 0 and 8.

Give the value or a description of two starting values for which the newton raphson method will fail to converge to either root of the equation.

cheers :)

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- December 30th 2009, 01:23 AMsillylillyNewton-Raphson method
An equation f(x) = 0 has two roots in the interval between 0 and 8.

Give the value or a description of two starting values for which the newton raphson method will fail to converge to either root of the equation.

cheers :) - December 30th 2009, 01:27 AMmr fantastic
Read practical considerations here: Newton's method - Wikipedia, the free encyclopedia

- December 30th 2009, 01:40 AMsillylilly
Yes I was just reading that before, only I don't understand how I can relate that directly to my problem?

- December 30th 2009, 07:13 AMHallsofIvy
If f(x)= 0 has two roots, then, by Rolle's theorem, there exist a value of x between those roots at which f' is 0. Quoting from the Wikipedia article mr. fantastic linked to

"4. It is clear from the formula for Newton's method that it will fail in cases where the derivative is zero. Similarly, when the derivative is close to zero, the tangent line is nearly horizontal and hence may "shoot" wildly past the desired root."