Linear Algebra : Linear Algebra

Study concepts, example questions & explanations for Linear Algebra

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Example Questions

Example Question #201 : Operations And Properties

Consider the following set of vectors

 

 

 

 

Is the the set linearly independent?

Possible Answers:

No

Yes

Not enough information

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 #281 : Linear Algebra

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

Possible Answers:

Five

Not enough information

There is no limit

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 #282 : Linear Algebra

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

Possible Answers:

Five

Six

Three

One

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 #204 : Operations And Properties

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

Possible Answers:

Five

Not enough information

Three

One

Two

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 #205 : Operations And Properties

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.

Example Question #21 : Linear Independence And Rank

If , what is ?

Possible Answers:

None of the other answers

Correct answer:

Explanation:

 is equal to the number of linearly independent columns of . The first and third columns are the same, so one of these columns is redundant in the column space of . The second column evidently cannot be a multiple of the first, since the second has two 's, and the first has none. Hence .

Example Question #21 : Linear Independence And Rank

Consider the polynomials 

True or false: these four polynomials form a basis for , the set of all polynomials with degree less than or equal to 3.

Possible Answers:

False

True

Correct answer:

True

Explanation:

A test to determine whether these matrices form a basis is to set up a matrix with each row comprising the coefficients of one polynomial, and performing row reductions until the matrix is in row-echelon form.   is a vector space of dimension 4, so these four polynomials will form a basis if and only if the resulting   matrix has rank 4. The initial matrix is:

Perform the following row operations:

The matrix is now in row-echelon form. Each row has a leading 1, so the matrix has rank 4, the dimension of . It follows that the given polynomials comprise a basis of .

Example Question #202 : Operations And Properties

Consider the polynomials:

True or false: these four polynomials form a basis for , the set of all polynomials with degree less than or equal to 3.

Possible Answers:

False

True

Correct answer:

False

Explanation:

Elements of a vector space form a basis if the elements are linearly independent and if they span the space - that is, every element in that space can be uniquely expressed as the sum of the elements. 

A test to determine whether these matrices form a basis is to set up a matrix with each row comprising the coefficients of one polynomial, and performing row reductions until the matrix is in row-echelon form.   is a vector space of dimension 4, so these four polynomials will form a basis if and only if the resulting   matrix has rank 4. The initial matrix is:

Perform the following row operations:

The matrix is now in row-echelon form. There is a row of zeroes at the bottom, so the rank of the matrix is 3. Therefore, the four polynomials are not linearly independent, and they do not form a basis for .

Example Question #21 : Linear Independence And Rank

, and .

True or false: these four matrices form a basis for the vector space , the set of  matrices.

Possible Answers:

False

True

Correct answer:

True

Explanation:

A test to determine whether these matrices form a basis is to set up a matrix with each row comprising the coefficients of one polynomial, and performing row reductions until the matrix is in row-echelon form.   is a vector space of dimension 4, so these four polynomials will form a basis if and only if the resulting   matrix has rank 4. The initial matrix is:

Perform the following row operations:

The matrix is now in row-echelon form. Each row has a leading 1, so the matrix has rank 4, the dimension of . It follows that the four matrices , and  comprise a basis of .

Example Question #21 : Linear Independence And Rank

In a 5 dimensional vector space, what is the maximum number of vectors you can have in a linearly dependent set?

Possible Answers:

No limit

Five

Zero

Ten

One

Correct answer:

No limit

Explanation:

Linearly dependent sets have no limit to the number of vectors they can have.

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