Linear algebra question about matrices

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Discussion Overview

The discussion revolves around determining the values of k for which a given matrix serves as the augmented matrix of a system with either infinitely many solutions or no solutions. Participants explore methods such as row reduction and determinant calculations to analyze the matrix.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests row reducing the matrix to upper triangular form to identify conditions for infinitely many solutions, noting that if f(k) = 0 and g(k) = 0, there are infinitely many solutions.
  • Another participant mentions setting the determinant equal to zero as a method to find k, but acknowledges that a zero determinant does not uniquely determine the nature of the solutions.
  • Some participants emphasize the need to consider the right-hand side of the augmented matrix when determining the conditions for infinitely many solutions.
  • There is a discussion about the confusion surrounding the row reduction process and how to correctly manipulate the rows to find k.
  • One participant suggests multiplying rows by specific expressions before performing row operations to facilitate finding k.

Areas of Agreement / Disagreement

Participants express differing views on the best approach to determine k, with no consensus on a single method. The discussion remains unresolved regarding the specific values of k for both cases of infinitely many solutions and no solutions.

Contextual Notes

Participants note limitations in their understanding of row reduction techniques and the implications of the determinant, indicating that further clarification may be needed to fully grasp the problem.

LaraCroft
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How would one determine the values of k such that the following matrix is the augmented matrix of a system with infinitely many solutions:

[ (k + 2) -2 1 | 2 ]
[ (k + 3) (k+ 3) 2 | 2 ]
[ (k + 2) -2 (k -1 ) | -3 ]

Also, how would I get all values of k such that the matrix for the same to be an augmented matrix of a system with no solutions?

It confuses me on how to find all possible values of k!

Thank you!:smile:
 
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LaraCroft said:
How would one determine the values of k such that the following matrix is the augmented matrix of a system with infinitely many solutions:

[ (k + 2) -2 1 | 2 ]
[ (k + 3) (k+ 3) 2 | 2 ]
[ (k + 2) -2 (k -1 ) | -3 ]

Also, how would I get all values of k such that the matrix for the same to be an augmented matrix of a system with no solutions?

It confuses me on how to find all possible values of k!

Thank you!:smile:
Try to row reduce it!
Reducing it to upper triangular form, so that you have only 0s below the main diagonal, you wind up with 0 0 f(k) | g(k). There is not a unique solution if f(k)= 0. There are an infinite number of solutions if g(k)= 0 also. (If f(k)= 0 and g(k) is not 0, then there is no solution.)
 
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I would have set the determinant equal to zero. Of course the determinate can be calculated via row reduction.
 
The problem with that is that if the determinant is 0, then the matrix equation may have infinitely many solutions or NO solution.
the question here was specifically to determine k so the equation has infinitely many solutions. You need to include the right hand side to determine that.
 
HallsofIvy said:
The problem with that is that if the determinant is 0, then the matrix equation may have infinitely many solutions or NO solution.
the question here was specifically to determine k so the equation has infinitely many solutions. You need to include the right hand side to determine that.

You can always substitute the roots obtained by the determinate back into the original system and then do row reduction. You can also put the system into upper triangular form while computing the determinate.
 
Ok...

Firstly, thank you everyone for responding...

Secondly, I am still not getting how to determine all the values of K, so that the matrix (call it A) is the augmented matrix of a system with infinitely many solutions. How would I find all values of K?

I understand that I need to row echelon it...but I think the way I am doing it is wrong...since the first entry cannot be 1...I start by doing Row 2 minus Row 1...and I I continue...however I am confused on what to do next in order to find k!

Apparently I should also be able to determine all values of k so that the matrix has a system with no solutions...

Thanks again:smile:
 
LaraCroft said:
Ok...
I understand that I need to row echelon it...but I think the way I am doing it is wrong...since the first entry cannot be 1...I start by doing Row 2 minus Row 1...and I I continue...however I am confused on what to do next in order to find k!

Before you do your subtraction multiply rows one and three by (K+3) and row 2 by (k+1)
 

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