Solution LI.C24 Robert Beezer
Theorem LIVRN suggests we analyze a matrix whose columns are the vectors from the set, \begin{equation*} A=\begin{bmatrix} 1 & 3 & 4 & -1\\ 2 & 2 & 4 & 2\\ -1 & -1 & -2 & -1\\ 0 & 2 & 2 & -2\\ 1 & 2 & 3 & 0 \end{bmatrix} \end{equation*} Row-reducing the matrix $A$ yields, \begin{equation*} \begin{bmatrix} \leading{1} & 0 & 1 & 2\\ 0 & \leading{1} & 1 & -1\\ 0 & 0 & 0 & 0\\ 0 & 0 & 0 & 0\\ 0 & 0 & 0 & 0 \end{bmatrix} \end{equation*} We see that $r=2\neq 4=n$, where $r$ is the number of nonzero rows and $n$ is the number of columns. By Theorem LIVRN, the set $S$ is linearly dependent.