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Re: Solving For 0

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  • Subject: [mg25827] Re: Solving For 0
  • From: "Paul Lutus" <nospam at>
  • Date: Sat, 28 Oct 2000 01:41:19 -0400 (EDT)
  • References: <8t64tq$>
  • Sender: owner-wri-mathgroup at

<bobmarley4u2c at> wrote in message news:8t64tq$ei1 at
> I noticed that when I use my Ti-89 or Mathematica 4.0, they solve for
> the roots very fast. I tried to create program simliar to that in C++,
> but I am having no luck. I tried the Iterative Method, which works, but
> it is extremly long. Then I tried Newton-Raphson method, which I got
> only to work for 3rd degree polynomial. It Newton-Rapson method just
> gives me the same answers after the 3rd degree.

In my long experience in programming, "divide and conquer" has been the best
and most robust approach to root finding. Design a binary search that begins
approaching the root and, on each pass through the root, reverses the sign
and size of the remaining distance. When the result falls below a chosen
epsilon, halt.

You must also realize that no root finder will find all roots of a complex
function on its own. You must have some idea of the locations of the roots,
or be willing to let the algorithm search for a long time.

> e-mail me at nganta82 at

In general, it is better to read the newsgroup. This way, if someone offers
defective advice, someone else will correct it. It's democracy at work.


Paul Lutus

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