Exercise 2.1.34

$\left[\begin{array}{cccc}\hfill 2& \hfill -1& \hfill 0& \hfill 0\\ \hfill -1& \hfill 2& \hfill -1& \hfill 0\\ \hfill 0& \hfill -1& \hfill 2& \hfill -1\\ \hfill 0& \hfill 0& \hfill -1& \hfill 2\end{array}\right]\left[\begin{array}{c}\hfill x_1\hfill \\ \hfill x_2\hfill \\ \hfill x_3\hfill \\ \hfill x_4\hfill \end{array}\right]=\left[\begin{array}{c}\hfill 1\hfill \\ \hfill 2\hfill \\ \hfill 3\hfill \\ \hfill 4\hfill \end{array}\right]$has the solution $\left[\begin{array}{c}\hfill x_1\hfill \\ \hfill x_2\hfill \\ \hfill x_3\hfill \\ \hfill x_4\hfill \end{array}\right]=\left[\begin{array}{c}\hfill 4\hfill \\ \hfill 7\hfill \\ \hfill 6\hfill \end{array}\right]$