Solving a system of equation with matrices

  • Context: Undergrad 
  • Thread starter Thread starter Mr Davis 97
  • Start date Start date
  • Tags Tags
    Matrices System
Click For Summary

Discussion Overview

The discussion revolves around solving a system of equations using matrices, specifically focusing on the row reduction process and the implications of the results obtained. Participants explore the validity of the solutions derived from the matrix representation of the equations and whether the equations can hold true simultaneously.

Discussion Character

  • Mathematical reasoning, Debate/contested, Homework-related

Main Points Raised

  • One participant presents a system of equations and a corresponding matrix, claiming to have performed row reduction that leads to specific values for the variables, but questions the validity of these results as they do not satisfy all original equations.
  • Another participant questions the accuracy of the values used in the matrix, specifically regarding the constants in the second equation, suggesting a potential inconsistency in the equations themselves.
  • There is a repeated inquiry about whether the first two equations can hold true simultaneously, indicating a possible fundamental issue with the system.
  • Suggestions are made to manipulate the equations, such as multiplying the second equation by -2 to compare it with the first, which leads to a contradiction.
  • Participants express uncertainty about the row reduction process and whether it should yield an inconsistent system, with one participant admitting to potential errors in their approach.

Areas of Agreement / Disagreement

Participants do not reach a consensus, as there are competing views regarding the validity of the equations and the results of the row reduction process. The discussion remains unresolved with respect to the correctness of the approach taken.

Contextual Notes

There are limitations regarding the assumptions made about the equations and their compatibility, as well as the potential for errors in the row reduction steps that have not been fully clarified.

Mr Davis 97
Messages
1,461
Reaction score
44
I have the following system of equations: ##2t-4s=-2;~-t+2s=-1;~3t-5s=3##. With them, I form the matrix
\begin{bmatrix}
2 & -4 & -2 \\
-1 & 2 & -1 \\
3 & -5 & 3
\end{bmatrix}
Which turns out to be row equivalent to
\begin{bmatrix}
1 & 0 & 11 \\
0 & 1 & 6 \\
0 & 0 & 0
\end{bmatrix}
so ##s=11,~t=6##. However, this satisfies only the first and third equation and not the second. Shouldn't it satisfy all of the equations, since I got a valid result from doing row reduction?
 
Last edited:
Physics news on Phys.org
Have you worked with ##A_{23}=-1## as in your second equation, or with ##A_{23}=-2## in your matrix?
And can the first two equations hold true simultaneously at all?
 
fresh_42 said:
Have you worked with ##A_{23}=-1## as in your second equation, or with ##A_{23}=-2## in your matrix?
And can the first two equations hold true simultaneously at all?
I fixed it. Am I doing the row reduction wrong? Should I be getting an inconsistent system?
 
Multiply the second equation by ##-2## and compare it with the first.
 
  • Like
Likes   Reactions: Mr Davis 97
fresh_42 said:
Multiply the second equation by ##-2## and compare it with the first.
2t - 4s = -2 and 2t - 4s = 2, which cannot be possible. So I guess I just did the row reduction wrong.
 

Similar threads

  • · Replies 11 ·
Replies
11
Views
6K
  • · Replies 1 ·
Replies
1
Views
4K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 12 ·
Replies
12
Views
2K
  • · Replies 7 ·
Replies
7
Views
3K
  • · Replies 24 ·
Replies
24
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
3K