\documentstyle[12pt]{siam} \begin{document} \addtolength{\baselineskip}{0.2\baselineskip} Consider the fixed-point problem \[ x_{n+1} = F(x), \] where \[ F(x) = \left(\begin{array}{c} (x)_1^2 - 3(x)_1(x)_2 + 50(x)_2 \\ (x)_1^2 + (x)_2^2 \end{array}\right) \] and $x_0 = \bigl((x_0)_1, (x_0)_2\bigr)^T = (0,1/100)^T$. Clearly, $(0,0)^T$ is a fixed-point for $F$. The iterations are exemplied in a Matlab script available at \begin{verbatim} http://www-math.bgsu.edu/~gwade/ma668/wadecode/superlinear.m \end{verbatim} From that script, the first six iterates produce \begin{center} \begin{tabular}{c|c} n & $\Vert x_{n+1}\Vert_2/\Vert x_n\Vert_2$ \\ \hline 0 & 50.0000 \\ 1 & 0.0071 \\ 2 & 35.0036 \\ 3 & 0.0018 \\ 4 & 34.6415 \\ 5 & 0.0001 \end{tabular} \end{center} {\bf Question:} How can we interpret this result in terms of our theory of fixed-point iterations? %% In case you're just learning LaTeX, here is how you'd write $F'(x)$ %% (of course you'll have to un-comment this line): %%\[ %% F'(x) = \left(\begin{array}{cc} %% 2(x)_1 - 3(x)_2 & -3(x)_1 + 50 \\ %% x(x)_1 & 2(x)_2 %% \end{array}\right) %%\] \end{document}