Linear Dependence/Independence

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Homework Help Overview

The problem involves determining whether a set of vectors in R^3 is linearly dependent or independent. The original poster presents a specific set of vectors and attempts to analyze their linear dependence using matrix representation and row reduction.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the implications of the row echelon form obtained from the matrix and question the conditions under which a set of vectors can be linearly independent in R^3. There is also inquiry into how to express a dependency equation based on the matrix results.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of linear dependence and independence. Some guidance has been provided regarding the formulation of dependency equations, but no consensus has been reached on the original poster's conclusion about linear independence.

Contextual Notes

There is a focus on the relationship between the number of vectors and their dimensionality, as well as the implications of the row rank in relation to the number of variables. The original poster's matrix includes a column of zeros, which is a point of contention in determining linear dependence.

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Homework Statement


Is the set S = {(3,-2,4),(4,6,-4),(3,6,-2),(-13,2,-18)} linearly dependent? If so, give a dependency equation.


Homework Equations





The Attempt at a Solution



I first placed the set S into a matrix equation
[3 4 3 -13
-2 6 6 2
4 -4 -2 -18]

then put it into rref:

[1 0 0 5.44 0
0 1 0 7.76 0
0 0 1 -9.24 0]

Since the final column is all zeros, is the system linearly independent?
 
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Can a set of more than 3 vectors in R^3 be linearly independent?
 
If the row rank is less than the number of variables then there has to be a parametric solution. How would I write a dependency equation, then?
 
This matrix,
[3 4 3 -13]
[-2 6 6 2]
[4 -4 -2 -18]
represents the vector equation c1*v1 + c2*v2 + c3*v3 + c4*v4 = 0. As a matrix equation this is Ac = 0, where the columns of A are your four vectors, and c = <c1, c2, c3, c4>^T.

Assuming that your work is correct and that you ended with the next matrix (I removed the 5th column of 0s),

[1 0 0 5.44]
[0 1 0 7.76]
[0 0 1 -9.24]

this matrix says that c1 + 5.44*c4 = 0, c2 + 7.76*c4 = 0, and c3 - 9.24*c4 = 0.
 

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