
Mark each statement as True or False. Justify each answer.
- a. If A is invertible and 1 is an eigenvalue for A, then 1 is also an eigenvalue of A−1.
- b. If A is row equivalent to the identity matrix I, then A is diagonalizable.
- c. If A contains a row or column of zeros, then 0 is an eigenvalue of A.
- d. Each eigenvalue of A is also an eigenvalue of A2.
- e. Each eigenvector of A is also an eigenvector of A2.
- f. Each eigenvector of an invertible matrix A is also an eigenvector of A−1.
- g. Eigenvalues must be nonzero scalars.
- h. Eigenvectors must be nonzero
vectors . - i. Two eigenvectors corresponding to the same eigenvalue are always linearly dependent.
- j. Similar matrices always have exactly the same eigenvalues.
- k. Similar matrices always have exactly the same eigen vectors.
- l. The sum of two eigenvectors of a matrix A is also an eigenvector of A.
- m. The eigenvalues of an upper triangular matrix A are exactly the nonzero entries on the diagonal of A.
- n. The matrices A and AT have the same eigenvalues, counting multiplicities.
- ○. If a 5 × 5 matrix A has fewer than 5 distinct eigenvalues, then A is not diagonalizable.
- p. There exists a 2 × 2 matrix that has no eigenvectors in ℝ2.
- q. If A is diagonalizable, then the columns of A are linearly independent.
- r. A nonzero vector cannot correspond to two different eigenvalues of A.
- s. A (square) matrix A is invertible if and only if there is a
coordinate system in which the transformation x i ↦ Ax is represented by a diagonal matrix. - t. If each vector ej in the standard basis for ℝn is an eigenvector of A, then A is a diagonal matrix.
- u. If A is similar to a diagonalizable matrix B, then A is also diagonalizable.
- v. If A and B are invertible n × n matrices, then AB is similar to BA.
- w. An n × n matrix with n linearly independent eigenvectors is invertible.
- x. If A is an n × n diagonalizable matrix, then each vector in ℝn can be written as a linear combination of eigenvectors of A.
(a)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
If A is invertible and 1 is an eigenvalue for A, then 1 is also an eigenvalue of
Explanation:
Consider the equation as follows:
Left-multiply with
Rewrite the equation as follows:
In this equation, x cannot be equal to zero. That is,
Therefore, 1 is an eigenvalue of
The given statement is true.
(b)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
If A is a row equivalent to the identity matrix I, then A is diagonalizable.
Explanation:
If A is a row that is equivalent to the identity matrix, then A is invertible.
Refer to Example 4 in section 5.3:
The given matrix is invertible. However, matrix A is not diagonalizable.
The given statement is false.
(c)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
If A contains a row or column of zeros, then 0 is an eigenvalue of A.
Explanation:
Theorem: The Invertible Matrix Theorem
Let Abe an
s. The number 0 is not an eigenvalue of A.
t. The determinant of A is not zero.
As given in the statement, if A contains a row or column of zeros, then A is not a row equivalent to the identity matrix.
Therefore, matrix A is not invertible.
Refer to the invertible matrix theorem, o is an eigenvalue of matrix A.
The given statement is true.
(d)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
Each eigenvalue of A is also an eigenvalue of
Explanation:
Consider a diagonal matrix whose eigenvalues are 1 and 2.
The value of
Then, the diagonal entries in the matrix are squaresof the eigenvalues of matrix A.
Therefore, the eigenvalues of
The given statement is false.
(e)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
Each eigenvector of A is also an eigenvector of
Explanation:
Consider a nonzero vector x.
The condition to be satisfied is
Left-multiply with A on both sides.
The derived equation shows that x is also an eigenvector of
The given statement is true.
(f)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
Each eigenvector of an invertible matrix A is also an eigenvector of
Explanation:
Consider a nonzero vector x.
The condition to be satisfied is
Left-multiply with
Matrix A is invertible and the eigenvalue of the matrix is nonzero.
The derived equation shows that x is also an eigenvector of
The given statement is true.
(g)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
Eigenvalues must be nonzero scalars.
Explanation:
For each singular square matrix, 0 will be the eigenvalue.
The given statement is false.
(h)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
Eigenvectors must be nonzero vectors.
Explanation:
Definition:
An eigenvector of an
Refer to the definition; an eigenvector must be nonzero.
The given statement is true.
(i)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
Two eigenvectors corresponding to the same eigenvalue are always linearly independent.
Explanation:
Refer to example 4 in section 5.1.
The eigenvalue for the given matrix is 2.
However, the calculated eigenvector for the eigenvalue is not linearly independent.
The given statement is false.
(j)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
Similar matrices always have exactly the same eigenvalues.
Explanation:
Theorem 4 (Section 5.2):
If
Refer to theorem 4; the given statement is correct.
The given statement is true.
(k)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
Similar matrices always have exactly the same eigenvectors.
Explanation:
Refer to example 3 in section 5.3.
Consider
The eigenvalues of the matrix are
The diagonalizable matrix is
Consider the matrix A is similar to the matrix D.
Suppose the eigenvalues of matrix D to be in column
Therefore, the given statement is incorrect.
The given statement is false.
(l)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
The sum of two eigenvectors of matrix A is also an eigenvector of A.
Explanation:
Consider a
The value of
The value of
Here,
Therefore, the given statement is incorrect.
The given statement is false.
(m)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
The eigenvalues of upper triangular matrix A are the exact nonzero entries on the diagonal of A.
Explanation:
Theorem 1: (Section 5.1):
The eigenvalues of a triangular matrix are the entries on its main diagonal.
In the given problem, the upper triangular matrix A has exactly nonzero entries. In reality, it is not necessary for that to be the case. Zero entries can also be available.
The given statement is false.
(n)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
Matrices A and
Explanation:
Apply the concept of determinant transpose property.
Show the determinant calculation of matrix A as follows:
Therefore, matrices A and
The given statement is true.
(o)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
If a
Explanation:
Refer to practice problem 3 in section 5.3.
Consider an identity matrix A that is
The given statement is false.
(p)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
A
Explanation:
Consider matrix A.
Matrix A rotates the vectors through
The value of Ax is not a multiple of x when x is a nonzero value.
The given statement is true.
(q)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
If A is diagonalizable, then the columns of A are linearly independent.
Explanation:
Consider a diagonal matrix A with 0 as diagonals.
Then, the columns of the diagonal matrix A are not linearly independent.
The given statement is false.
(r)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
A nonzero vector cannot correspond to two different eigenvalues of A.
Explanation:
Consider the following example:
Equate both the values of
Suppose x cannot be equal to zero, that is,
Therefore, for a nonzero vector, two different eigenvalues are the same.
The given statement is true.
(s)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
A (square) matrix A is invertible if and only if there is a coordinate system in which the transformation
Explanation:
Theorem 8 (Section 5.4):
Diagonal Matrix Representation:
Suppose
Consider a singular matrix A that is diagonalizable.
Refer to the theorem; the transformation
The given statement is false.
(t)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
If each vector
Explanation:
Refer to the definition of matrix multiplication.
Show the multiplication of matrix A with I as follows:
If the values are considered as
Then, matrix A becomes a diagonal matrix with the diagonal entries of
Therefore, the given statement is correct.
The given statement is true.
(u)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
If A is similar to diagonalizable matrix B, then A is also diagonalizable.
Explanation:
Consider matrix B.
For a diagonalizable matrix:
Here, D is a diagonalizable matrix.
Consider matrix A. Write the equation as follows:
Substitute
Therefore, matrix A is diagonalizable.
The given statement is true.
(v)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
If A and B are invertible
Explanation:
If the matrix B is invertible, the value of AB is similar to
This calculated value is equal to BA.
The given statement is true.
(w)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is false.
Explanation of Solution
Given statement:
An
Explanation:
Theorem 5 (Section 5.3):
The diagonalization theorem:
An
In fact,
Refer to the theorem; the
The given statement is false.
(x)

To mark: Each statement as true of false.
To justify: The answer.
Answer to Problem 1SE
The given statement is true.
Explanation of Solution
Given statement:
If A is an
Explanation:
Theorem 5 (Section 5.3):
The diagonalization theorem:
An
In fact,
A is diagonalizable if and only if A has n linearly independent eigenvectors
Refer to basis theorem:
That is, each vector in
The given statement is true.
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