N(A) and R(A) in terms of their basis

  • Thread starter Thread starter DryRun
  • Start date Start date
  • Tags Tags
    Basis Terms
Click For Summary

Homework Help Overview

The problem involves expressing the null space and row space of a given matrix A in terms of their basis vectors. Participants are exploring how to format their answers correctly while discussing the concepts of null space and row space.

Discussion Character

  • Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants discuss different ways to express the null space, including vector forms and set notation. There is also consideration of how to articulate the answers clearly and effectively for presentation.

Discussion Status

Some participants have offered guidance on acceptable formats for expressing the null space and row space, while others are reflecting on the importance of clarity in their explanations. Multiple interpretations of how to present the answers are being explored.

Contextual Notes

There is mention of potential confusion regarding established answer formats and the expectations of the instructor. The discussion includes varying opinions on the necessity of written explanations accompanying the vector representations.

DryRun
Gold Member
Messages
837
Reaction score
4

Homework Statement


The matrix A =
1 1 1 1
-1 0 1 0
1 2 3 2

Express null space and row space of A in terms of their basis vectors.

2. The attempt at a solution

I have found the null space to be: x3 [1 -2 1 0]^T + x4 [0 -1 0 1]^T.

But my problem is how do i write the final answer correctly? Should i just write the answer as above? Or should i just write it this way: [1 -2 1 0]^T and [0 -1 0 1]^T

I did a search online and ended up with this way to present the solution, but there are so many variations, I'm confused.
{[1 -2 1 0]^T, [0 -1 0 1]^T}.

Which is the correct established answer format?

For the row space, i gave the answer like this:
[ 1 1 1 1] and [0 1 2 1]

Or should it be like this?: {[ 1 1 1 1], [0 1 2 1]}
 
Last edited:
Physics news on Phys.org
The problem says to "Express the null space of A in terms of its basis vectors.
So I would say you can give the answer in either of two ways:
1) "All vectors in the null space of A are of the form [itex]x_1\begin{bmatrix}1 \\ -2 \\ 1 \\ 0\end{bmatrix}+ x_2\begin{bmatrix}0 \\ -1 \\ 0 \\ 1\end{bmatrix}[/itex]"
or
2) "A basis for the null space is [itex]\{\begin{bmatrix}1 \\ -2\\ 1\\ 0 \end{bmatrix}, \begin{bmatrix}0 \\ -1 \\ 0 \\ 1\end{bmatrix}\}[/itex]".

But the words explaining what you answer means are as important as your vectors.
 
Thanks for your help, HallsofIvy. I will keep your advice in mind for my exams.
 
Yep- actually writing out full sentence answers is likely to send your teacher into shock!
 
You can also say that the null space is span{(v1), (v2)}.
 

Similar threads

Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 6 ·
Replies
6
Views
1K
Replies
2
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
Replies
8
Views
1K
  • · Replies 7 ·
Replies
7
Views
2K