Solution LI.C25 Robert Beezer
Theorem LIVRN suggests we analyze a matrix whose columns are the vectors from the set, \begin{equation*} A=\begin{bmatrix} 2 & 4 & 10 \\ 1 & -2 & -7 \\ 3 & 1 & 0 \\ -1 & 3 & 10 \\ 2 & 2 & 4 \end{bmatrix} \end{equation*} Row-reducing the matrix $A$ yields, \begin{equation*} \begin{bmatrix} \leading{1} & 0 & -1 \\ 0 & \leading{1} & 3 \\ 0 & 0 & 0 \\ 0 & 0 & 0 \\ 0 & 0 & 0 \end{bmatrix} \end{equation*} We see that $r=2\neq 3=n$, where $r$ is the number of nonzero rows and $n$ is the number of columns. By Theorem LIVRN, the set $S$ is linearly dependent.