Linear Algebra : Linear Mapping

Study concepts, example questions & explanations for Linear Algebra

varsity tutors app store varsity tutors android store

Example Questions

Example Question #501 : Operations And Properties

Let  be a function such that . Is it possible for  to have a rank of  and a null space with dimension ?

Possible Answers:

no

not enough information

yes

Correct answer:

no

Explanation:

The rank and the dimension of the null space must add up to the dimension of the domain from the formula

where  is the dimension of the domain,

 is the dimension of the null space,

and  is the rank.

For this problem the dimension of the domain () is . So

From the problem statement, we want to consider  and But if we plug this into the formula we get

Hence the equation for dimension doesn't hold. 

 

Example Question #881 : Linear Algebra

A mapping is said to be onto (sometimes called surjective) if it's image is the entire codomain.

Is the linear map such that onto?

Possible Answers:

Not enough information

Yes

No

Correct answer:

Yes

Explanation:

Yes,  is onto because any vector in the codomain, ,  is the image of a vector from the domain.

Example Question #882 : Linear Algebra

A mapping is said to be onto (sometimes called surjective) if it's image is the entire codomain.

Is the linear map  such that  onto?

(This map is sometimes called a projection, specifically a projection onto the xy plane.)

Possible Answers:

Not enough information

Yes

No

Correct answer:

Yes

Explanation:

This mapping is onto. For any given vector in the codomain, , there is a corresponding vector in the domain, .

Example Question #883 : Linear Algebra

Is the linear map  such that  onto?

(Note this is sometimes called the identity map because it maps every vector to itself)

Possible Answers:

Yes

No

Not enough information

Correct answer:

Yes

Explanation:

The answer is yes, the mapping is onto. The image of is which is the codomain.

Example Question #25 : Linear Mapping

A mapping is said to be onto (sometimes called surjective) if it's image is the entire codomain.

Is the linear map  such that  onto?

Possible Answers:

Not enough information

Yes

No

Correct answer:

No

Explanation:

First we need to find the image of Any vector in the image of has the form .

Treat and like arbitrary constants. Then the image of is the subspace spanned by the set of vectors This subspace has a basis of 2 vectors. Therefore it has dimension of .

The image of does not span the whole codomain, , because the image does not have the same dimension as the codomain, .

 

Another way to do this problem is recognize that the domain,, has dimension . Therefore, the linear map can have an image of  with dimension of at most 2. But the codomain has dimension . Since , can't be onto.

Example Question #884 : Linear Algebra

A mapping is said to be onto (sometimes called surjective) if it's image is the entire codomain.

Is the linear map such that  onto?
(Note this is called the zero mapping)

Possible Answers:

No

Yes

Not enough information

Correct answer:

No

Explanation:

No, is not onto. This is because the image of is only the zero vector, not all of

Example Question #885 : Linear Algebra

A mapping is said to 1-to-1 (sometimes called injective) if no two vectors in the domain go to the same vector in the image of the mapping.

Is the linear map  such that  1-to1?

Possible Answers:

Yes

No

Not enough information

Correct answer:

Yes

Explanation:

The linear map, , is 1-to-1 because no vector in the codomain is the output of two different vectors in the domain.

Example Question #21 : Linear Mapping

There are relationships between the dimension of the null space (sometimes called kernal) and if a function is 1-to-1

The dimension of a linear map's null space is zero. Is the linear map 1-to-1?

Possible Answers:

No

Yes

Not enough information

Correct answer:

Yes

Explanation:

A linear map is always 1-to-1 if the null space has dimension zero.

The converse of this statement is also true. A linear map is 1-to-1 if the null space has dimension 0.

Example Question #886 : Linear Algebra

A mapping is said to 1-to-1 (sometimes called injective) if no two vectors in the domain go to the same vector in the image of the mapping.

Is the linear map such that  1-to1?
(Note this is called the zero mapping)

Possible Answers:

No

Not enough information

Yes

Correct answer:

No

Explanation:

The linear map, is not 1-to-1 because more than one vector goes to the zero vector. In fact, all vectors go to the same vector for the zero mapping!

For example, the vector and both go to the same vector. Thus is not 1-to-1

Example Question #887 : Linear Algebra

A linear map has a null space that is spanned by the vectors,

and . is this function 1-to-1?

Possible Answers:

Yes

Not enough information

No

Correct answer:

No

Explanation:

This linear mapping is not 1-to-1. We know this because the null space is spanned by two vectors. Therefore the null space has dimension . A linear map is 1-to-1 only if it has a null space with dimension zero. This linear map doesn't have a null space of dimension zero, therefore it is not 1-to-1.

Learning Tools by Varsity Tutors