Linear Algebra : Linear Independence and Rank

Study concepts, example questions & explanations for Linear Algebra

varsity tutors app store varsity tutors android store

Example Questions

Example Question #11 : Linear Independence And Rank

 

 

Consider the following set of three vectors:

where 

 

Is the set linearly independent?

Possible Answers:

Yes

No

Not enough information

Correct answer:

No

Explanation:

Since  can be written as a linear combination of of  and  then the set cannot be linearly independent.

Example Question #11 : Linear Independence And Rank

Does the following row reduced echelon form of a matrix represent a linearly independent set?

 

Possible Answers:

Not enough information

No

Yes

Correct answer:

No

Explanation:

The set is linearly dependent because there is a row of all zeros.

Notice that having columns of all zeros does not tell if the set is linearly independent or not.

Example Question #11 : Linear Independence And Rank

Determine the row rank of the matrix

Possible Answers:

Correct answer:

Explanation:

To determine the matrix, we turn the matrix into reduced row echelon form

By adding  times the first row to the second we get

And find that the row rank is 

Example Question #14 : Linear Independence And Rank

Determine the row rank of the matrix

Possible Answers:

Correct answer:

Explanation:

To determine the row rank of the matrix we reduce the matrix into reduced echelon form.

First we add  times the 1st row to the 2nd row

add  times the 1st row to the 3rd row

Switch the 2nd row and the 3rd row

multiply the 2nd row by

add  times the 2nd row to the 1st row

And we find that the row rank is 

Example Question #15 : Linear Independence And Rank

 

 

Consider the following set of vectors

 

 

 

Is the the set linearly independent?

Possible Answers:

Not enough information

No.

Yes.

Correct answer:

Yes.

Explanation:

Yes, the set is linearly independent. There are multiple ways to see this

Way 1) Put the vectors into matrix form,

The matrix is already in reduced echelon form. Notice there are three rows that have a nonzero number in them and we started with 3 vectors. Thus the set is linearly independent.

Way 2) Consider the equation

If when we solve the equation, we get  then it is linearly independent. Let's solve the equation and see what we get.

Distribute the scalar constants to get

Thus we get a system of 3 equations

Since the vectors are linearly independent.

Example Question #14 : Linear Independence And Rank

Consider the following set of vectors

 

 

 

 

Is the the set linearly independent?

Possible Answers:

No

Not enough information

Yes

Correct answer:

No

Explanation:

The vectors have dimension 3. Therefore the largest possible size for a linearly independent set is 3. But there are 4 vectors given. Thus, the set cannot be linearly independent and must be linearly dependent

Another way to see this is by noticing that  can be written as a linear combination of the other vectors:

Example Question #12 : Linear Independence And Rank

In a vector space with dimension 5, what is the maximum number of vectors that can be in a linearly independent set?

Possible Answers:

There is no limit

Five

Not enough information

Two

Ten

Correct answer:

Five

Explanation:

The dimension of a vector space is the maximum number of vectors possible in a linearly independent set. (notice you can have linearly independent sets with 5 or less, but never more than 5)

Example Question #13 : Linear Independence And Rank

What is the dimension of the space spanned by the following vectors:

Possible Answers:

One

Five

Three

Six

Not enough information

Correct answer:

Three

Explanation:

Since there are three linearly independent vectors, they span a 3 dimensional space. 

Notice that the vectors each have 5 coordinates to them. Therefore they actually span a 3 dimensional subspace of a 5 dimensional space.

Example Question #14 : Linear Independence And Rank

What is the dimension of the space spanned by the following vectors:

Possible Answers:

Five

Three

Not enough information

Two

One

Correct answer:

Three

Explanation:

Since there are three linearly independent vectors, they span a 3 dimensional space.

Notice that the vectors each have 5 coordinates to them. Therefore they actually span a 3 dimensional subspace of a 5 dimensional space.

Example Question #18 : Linear Independence And Rank

True or False: If a  matrix  has  linearly independent columns, then .

Possible Answers:

True

False

Correct answer:

True

Explanation:

Since  is a  matrix, . Since  has three linearly independent columns, it must have a column space (and hence row space) of dimension , causing  by the definition of rank. Hence.

Learning Tools by Varsity Tutors