MML Discourse archived in May, 2026

Column space and null space of a matrix

mark

Let

M = \left[\begin{array}{rrrrr} 1 & 2 & 3 & 4 & 5 \\ 6 & 7 & 8 & 9 & 10 \\ 11 & 12 & 13 & 14 & 15 \end{array}\right]
  1. Find a basis for the column space of M.
  2. Find a basis for the null space of M.

You should absolutely use SageMath to compute the RREF of this matrix.

User 009

rref:

\begin{bmatrix} 1 & 0 & -1 & -2 & -3 \\ 0 & 1 & 2 & 3 & 4 \\ 0 & 0 & 0 & 0 & 0 \end{bmatrix}

Homogeneous System:

v-x-2y-3z = 0 \\ w+2x+3y+4z = 0
  1. Find a basis for the column space of M.
\begin{bmatrix} 1 \\ 0 \\ 0 \\ \end{bmatrix} \begin{bmatrix} 0 \\ 1 \\ 0 \\ \end{bmatrix}
  1. Find a basis for the null space of M.
v-x-2y-3z = 0 \\ v = x-+2y+3z\\ \\ w+2x+3y+4z = 0\\ w = -2x-3y-4z\\ \\ x = x\\ y = y\\ z = z

Thus:

\begin{bmatrix} v \\ w \\ x \\ y \\ z \end{bmatrix} =x \begin{bmatrix} 1 \\ -2 \\ 1 \\ 0 \\ 0 \end{bmatrix} y \begin{bmatrix} 2 \\ -3 \\ 0 \\ 1 \\ 0 \end{bmatrix} z \begin{bmatrix} 3 \\ -4 \\ 0 \\ 0 \\ 1 \end{bmatrix}
mark

Nice! Next question for working on part 2: Can you translate this to a homogeneous system?