Given two points x1 and 2, such that
y(x1) y(x2) < 0
(that is, such that they surround the root), perform linear interpolation
y = y(x1) + (y(x2) - y(x1))/(x2 - x1) (x - x1)
Set y = 0 and solve for x. This yields an iterative step. Hey, you did not intend me to solve that equation for you, did you now? Well, ok, I will relent just this once:
x = x1 - y(x1) (x2 - x1) / (y(x2) - y(x1))
Copyright (c) 1997 R. I. 'Sciibor-Marchocki last modified on Tuesday 06-th
May 1997.