eneral implementation in the nth root-finding examples.
            For example, it uses a polynomial approximation to generate a better
            guess than dividing the exponent by three, and can avoid the complex
            checks in <a class="link" href="../roots_deriv.html#math_toolkit.roots_deriv.newton">Newton-Raphson
            iteration</a> required to prevent the search going wildly off-track.
            For a known precision, it may also be possible to fix the number of iterations,
         