###### Item1.2.5.1.c

The reduced row echelon form is

\begin{equation*} \left[\begin{array}{rrrr|r} 1 \amp 0 \amp -1 \amp 0 \amp 2 \\ 0 \amp 1 \amp -2 \amp 0 \amp -3 \\ 0 \amp 0 \amp 0 \amp 1 \amp -1 \\ 0 \amp 0 \amp 0 \amp 0 \amp 0 \end{array}\right]\text{,} \end{equation*}

which gives the equations

\begin{equation*} \begin{aligned} x_1 \amp = 2 + x_3 \\ x_2 \amp = -3 + 2x_3 \\ x_4 \amp = -1 - x_3. \\ \end{aligned} \end{equation*}

This shows that $$x_3$$ is a free variable and $$x_1\text{,}$$ $$x_2\text{,}$$ and $$x_4$$ are basic variables. There are therefore infinitely many solutions.

in-context