All Linear Algebra Resources
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 )
Yes
Not enough information
No
No
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?
Not enough information
No
Yes
Yes
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 )
Yes
Not enough information
No
Yes
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 ?
The zero vector
The space spanned by the vector
The space spanned by the vector
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 ?
The vector
The line
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 ?
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.
True
False
True
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 .
False
True
False
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 .
True
False
True
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 .
True
False
False
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 .