Linear Algebra : Linear Mapping

Study concepts, example questions & explanations for Linear Algebra

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Example Questions

Example Question #31 : Linear Mapping

A linear map  has a rank of 3. Is the linear map, ,  1-to-1?

(Hint- Use the formula where

is the dimension of the domain

is the dimension of the null space

is the rank of the linear map )

Possible Answers:

Yes

Not enough information

No

Correct answer:

No

Explanation:

The answer is no because the dimension of the null space is not zero. This comes from the equation

We know that the domain is which has dimension of . Therefore

Also from the problem statement .

Plugging these into the equation gives

Since the dimension of the null space is  and not , then the function can't be 1-to-1.

Example Question #31 : Linear Mapping

A linear map has a null space consisting of only the zero vector. Is 1-to-1?

Possible Answers:

Not enough information

No

Yes

Correct answer:

Yes

Explanation:

If the dimension of the null space is zero then the linear map is 1-to-1.

For this problem, we are told the null space is only the zero vector. Therefore the null space has dimension . Since the null space has dimension , then is 1-to-1.

Example Question #33 : Linear Mapping

A linear map  has a rank of 4. Is the linear map, ,  1-to-1?

(Hint- Use the formula where

is the dimension of the domain

is the dimension of the null space

is the rank of the linear map )

Possible Answers:

Yes

Not enough information

No

Correct answer:

Yes

Explanation:

The answer is yes because the dimension of the domain and the rank are equal. This implies that the dimension of the null space is zero.

This comes from the equation

We know that the domain is which has dimension of . Therefore

Also from the problem statement .

Plugging these into the equation gives

Since the dimension of the null space is  then the function is 1-to-1.

Notice that whenever , then is always zero. Thus whenever , the linear mapping is 1-to-1.

Example Question #32 : Linear Mapping

The null space (sometimes called the kernal) of a mapping is a subspace in the domain such that all vectors in the null space map to the zero vector.  

Consider the mapping  such that .

What is the the null space of ?

Possible Answers:

The zero vector

The space spanned by the vector

Correct answer:

The space spanned by the vector

Explanation:

Any vector in the null space satisfies .

Therefore we get the following equation:

 

Thus . Hence the null space is any vector in form where  is any real number. Therefore, any point on the line  gets mapped to the zero vector in  

Example Question #34 : Linear Mapping

This problem deals with the zero map. I.e the map that takes all vectors to the zero vector.

Consider the mapping  such that .

What is the the null space of ?

Possible Answers:

The vector 

The line 

Correct answer:

Explanation:

The zero map takes all vectors to the zero vector. Therefore, the entire domain of the map is the null space. The domain of this map is . Thus  is the null space.

Example Question #35 : Linear Mapping

This problem deals with the zero map. I.e the map the takes all vectors to the zero vector.

Consider the mapping  such that .

What is the the rank of ?

Possible Answers:

Correct answer:

Explanation:

The image of the the zero map is the zero vector. A single vector has dimension . Therefore the dimension of the image is zero. Hence the rank is zero. 

Example Question #514 : Operations And Properties

 refers to the set of all functions with domain and range a subset of .

Define the transformation to be

True or false:  is a linear transformation.

Possible Answers:

True

False

Correct answer:

True

Explanation:

For  to be a linear transformation, it must hold that 

and

for all  in the domain of  and and for all scalar .

Let .

and , so

By the sum rule for finite sequences,

By the derivative sum rule,

The first condition is met.

Let and be a scalar.

By the scalar product rule for finite sequences,

By the scalar product rule for derivatives,

The second condition is met.

is a linear transformation.

Example Question #33 : Linear Mapping

 refers to the set of all functions that are continuous on 

Define the linear mapping  as follows:

True or false:  is in the kernel of .

Possible Answers:

False

True

Correct answer:

False

Explanation:

The kernel of a linear transformation  is the subset of the domain of  that maps into the zero of its range, so, by definition,  if and only if

To determine whether this is true or false, evaluate the integral:

, so .

Example Question #34 : Linear Mapping

 refers to the set of all functions that are continuous on

Define the linear mapping  as follows:

True or false:  is in the kernel of .

Possible Answers:

True

False

Correct answer:

True

Explanation:

The kernel of a linear transformation  is the subset of the domain of  that maps into the zero of its range. It follows that  if and only if

To determine whether this is true or false, evaluate the integral:

Therefore, .

Example Question #32 : Linear Mapping

True or false: If  is a linear mapping, and  is a vector space, then  is a subspace of .

Possible Answers:

True

False

Correct answer:

False

Explanation:

For example, if  is the space of all vectors in  of the form , and  is the space of all vectors in  the form , then  is a linear mapping, but  is not a subset of , let alone a subspace of .

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