Let be a polynomial and be `maxroot` the maximal modulus of
the root of . From we may derive a the *unitary polynomial* such that the
roots of have a modulus lower or equal to 1 and if is a root
of then `maxroot` is a root of .

Let which may also be written as where is some fixed point.

Let a range for and let be the mid point of the
range. We consider the square in the complex plane centered at
and whose edge length is . Let be the length of the
half-diagonal of this square.
If

then the polynomial has no root in the square [1]. This procedure may be used for univariate polynomial, with polynomial with interval coefficients or with parametric poynomial. For example it is very efficient for solging the Wilkinson polynomial.