So i have the following subspace
r − s − 2t − u
−r + 2s + 5t + 2u
s + 3t + u
3r + s + 5u
$$\begin{bmatrix}1 & -1 & -2 & -1 \\ -1 & 2 & 5 & 2 \\ 0 & 1 & 3 & 1 \\ 3 & 1 & 0 & 5 \\ \end{bmatrix}$$ These four equations are all put into square brackets. There are no zero's in the questions equal to the equations. This is a past exam question .
And i need to find the basis. I know that r,s,t,u are all scalars. I was thinking of decomposing these equations into variables and numbers, but i am not sure.
How would i find the basis ? Could somebody help me ? I was thinkig it might have something to do with the span.
YES i already asked the question. Please to not mark it as a duplicate.. I asked it again so more people can see it and maybe help me.