Exercise 3.1.28

$A=\left[\begin{array}{ccc}1\hfill & 1\hfill & 0\hfill \\ 1\hfill & 0\hfill & 0\hfill \\ 0\hfill & 1\hfill & 0\hfill \end{array}\right]$and $\left[\begin{array}{ccc}1\hfill & 1\hfill & 2\hfill \\ 1\hfill & 0\hfill & 1\hfill \\ 0\hfill & 1\hfill & 1\hfill \end{array}\right]$do not have $\left[\begin{array}{c}1\hfill \\ 1\hfill \\ 1\hfill \end{array}\right]$ in $C(A).A=\left[\begin{array}{ccc}1\hfill & 2\hfill & 0\hfill \\ 2\hfill & 4\hfill & 0\hfill \\ 3\hfill & 6\hfill & 0\hfill \end{array}\right]$ has $C(A)=$ line in $R^3.$