Re: A question on Newton's Method

David M wrote:
> FORTRAN is the
> language I'm using since its easier then some of the others out
> there

If you're just starting out then I recommend you use a more appropriate
language, like Mathematica (commercial) or OCaml (free). Both of these
languages let you concentrate on the problem at hand, rather than having to
mess about with computer-specific problems. They are also much easier to
learn and use and they will allow you to solve much more difficult and
interesting problems.

> someone pointed out that using the quadratic equation is not
> exactly stable when it comes to computers.

Yes, evaluating the expressions for solutions to a quadratic as they are
taught at school is not numerically stable when you are using floating
point arithmetic. This is actually pedagogical example used to teach
numerical robustness.

> So doing some looking
> around I found a book called "Applied Numerical Methods" that showed
> how Newton's Method worked. But it's a bit vauge since its meant for
> someone a bit more advanced then I am (I'm in Calc 2).

If you are referring to the iterative Newton-Raphson method then that is not
the conventional way to find the roots of a quadratic robustly. You should
simply rearrange the expressions into a robust form.

--
Dr Jon D Harrop, Flying Frog Consultancy
http://www.ffconsultancy.com
.

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