# Set of vectors, linearly dependent or independent?

• Mutaja
In summary: Period. That's the one good thing you did ...showed that they were dependent and showed how.In summary, using the Gauss-Jordan method, it is determined that the following sets of vectors are linearly independent: A) (1,1) and (1,3), B) (1,2,3) and (2,1,3). Additionally, it is noted that it is impossible for three 2-vectors to be linearly independent.
Mutaja

## Homework Statement

Check if the following set of vectors are linearly dependent or independent:

A) V1= $\stackrel{1}{1}$ V2= $\stackrel{1}{3}$

B) V1= $\stackrel{\stackrel{1}{2}}{3}$ V2= $\stackrel{\stackrel{2}{1}}{3}$

C) V1= $\stackrel{1}{3}$ V2= $\stackrel{2}{1}$ V3= $\stackrel{-1}{2}$

## Homework Equations

Gauss-Jordan, equation with two unknowns.

## The Attempt at a Solution

A) x1 * V1 + x2*v2 = 0

if x1 AND x2 = 0, then they're linearly independent. If not, they're linearly dependent.

$\stackrel{1}{1}$ $\stackrel{1}{3}$ * $\stackrel{X1}{X2}$ = 0

Using gauss jordan I get: $\stackrel{1}{1}$ $\stackrel{1}{3}$ $\stackrel{0}{0}$ -> $\stackrel{1}{0}$$\stackrel{1}{2}$$\stackrel{0}{0}$-> $\stackrel{1}{0}$$\stackrel{1}{1}$$\stackrel{0}{0}$-> $\stackrel{1}{0}$$\stackrel{0}{1}$$\stackrel{0}{0}$ which gives me x1 = 0, x2 = 0.

X1+ X2 = 0
X1 + 3X2 = 0

-2X2 = 0 -> X2 = 0
X1 = 0.

Both X1 and X2 has to be 0 -> linearly independent.

B) X1*V1 + X2*V2 = 0

Using the same method -> Gauss Jordan. I end up with the same, X1 an X2 has to be 0 -> linearly independent.

Please do let me know if I should write all my work here as well. Leaving it as it is for now as it takes 15 minutes, and I've done the exact same steps as above.

C) Here we can see that V1 - V2 = V3, therefore they are linearly dependent.

Is this sufficient to "check" if they're linearly dependent or independent, or do I have to do more work? If so, do you have any tips on how to proceed with three vectors?

Also, any tips regarding how to write vectors or matrices efficiently with latex or what it's called, please let me know. I'll be more than happy to include more of my work if I can do it somewhat efficiently.

Thanks for any input.

Is this sufficient to "check" if they're linearly dependent or independent, or do I have to do more work?
To show the set is dependent you need only show a single case of dependence ... showing independence is the one that involves hard work.

If so, do you have any tips on how to proceed with three vectors?
Bottom of page:
http://www.math.oregonstate.edu/hom...ulusQuestStudyGuides/vcalc/lindep/lindep.html

Also, any tips regarding how to write vectors or matrices efficiently with latex or what it's called, please let me know. I'll be more than happy to include more of my work if I can do it somewhat efficiently.

you can use the "matrix" environment:$$v_1=\begin{pmatrix}1\\ 1 \end{pmatrix},\; v_2=\begin{pmatrix}1\\ 3 \end{pmatrix}$$
... hit the "quote" button to see what I did :)
http://www.math-linux.com/latex-26/faq/latex-faq/How-to-write-matrices-in-Latex

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1 person
Hmmm. I have no big problem with your answers. But they aren't 'optimum' (in some ways).
First V1 = ( 1,1), V2 = (1,3) ...these are NOT the same as (1,1,0) and (1,3,0)!
Second by simple inspection, there is no number x which will multiply (1,1) and produce (1,3). This is obvious...all you can get is (x,x). So, the set is independent.
Third the same thing is obviously true for (1,2,3) and (2,1,3)...there is exactly one number (scalar multiplication, of course) which will get you from the first element of vector 1 to the first element of vector 2. That number is 2... 2*(1,2,3) = (2,4,6) which is, again obviously, NOT (2,1,3). so also independent.
Fourth. It is IMPOSSIBLE to have MORE than 2 independent vectors in any (real) 2-vector. You didn't have to do any math to know that C could not be a set of three independent 2-vectors. Not possible. You can not have more than n independent n-vectors (over the real vector spaces).

## 1. What is a set of vectors?

A set of vectors is a collection of two or more vectors that are arranged in a certain order.

## 2. What does it mean for vectors to be linearly dependent?

Vectors are linearly dependent if one or more of the vectors in the set can be written as a combination of the other vectors in the set. In other words, they are not all independent of each other.

## 3. How do you determine if a set of vectors is linearly independent?

To determine if a set of vectors is linearly independent, you can use the determinant method. If the determinant of the matrix formed by the vectors is non-zero, then the vectors are linearly independent. Another method is to see if there is a non-trivial solution to the equation Ax=0, where A is the matrix formed by the vectors and x is a column vector of coefficients.

## 4. Why is it important to know if a set of vectors is linearly dependent or independent?

Knowing if a set of vectors is linearly dependent or independent is important in many areas of mathematics and science. It helps us to understand relationships between different vectors and to solve equations involving these vectors. It is also used in fields such as physics, engineering, and computer science.

## 5. Can a set of two or more vectors be both linearly dependent and independent?

No, a set of vectors can only be either linearly dependent or independent. If a set of vectors is linearly dependent, it means that some of the vectors are not needed because they can be expressed as a linear combination of the other vectors. If a set of vectors is linearly independent, it means that all of the vectors are necessary and cannot be expressed as a linear combination of each other.

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