Explain why the function m(v) used in the development of the power method in Example 7.3.7 is not a continuous function, so statements like m(x_n) → m(x) when x_n → x are not valid. Nevertheless, if lim_{n→∞} x_n ≠ 0, then lim_{n→∞} m(x_n) ≠ 0.
Consider
x_n = \begin{pmatrix}1 − 1/n\\ -1\end{pmatrix} → x = \begin{pmatrix}1\\-1\end{pmatrix},
but m(x_n) = −1 for all n = 1, 2, . . . , and m(x) = 1, so m(x_n) \cancel{→} m(x). Nevertheless, if lim_{n→∞} x_n ≠ 0, then lim_{n→∞} m (x_n) ≠ 0 because the function \tilde{m}(v) = |m(v)| = ||v||_∞ is continuous.