I have to show that $a_4$ is in the span of the other 3 vectors $a_1,a_2,a_3$
\begin{bmatrix} 2 &1 & 3\\ 3 & -1 & 4 \\ 1 & 2 & -1 \\ 4 & 4 & 3 \\ 0 & 3 & 5 \\ & \end{bmatrix} My Maple code: with (LinearAlgebra);
A := <<2, 1, 3>,<3, -1, 4>,<1, 2, -1>,<4, 4, 3>,<0, 3, 5>>; Then i use ReducedRowEchelon to get the linear combination which is M=:{{1,0,0},{0,1,0},{0,0,1},{0,0,0}, {0,0,0} }.
How do i prove that $a_4$ which is {-3,-6,5,2,7} is in the span of the other 3 vectors?