Matrix Diagonalization and Similar Matrices - Question Bank

1. What is the condition for a matrix A to be diagonalizable by a unitary matrix U (i.e., A = UDU⁻¹ where U is unitary)?
A) A must be symmetric.
B) A must be normal (A*A = AA*).
C) A must have distinct eigenvalues.
D) A must be invertible.
2. If A is similar to B, then the eigenvalues of A are the same as the eigenvalues of B.
A) True
B) False
C) Only if P is the identity matrix
D) Only if A and B are diagonal
3. What is the spectral theorem regarding diagonalizable matrices?
A) A matrix is normal if and only if it is unitarily diagonalizable.
B) A matrix is diagonalizable if and only if it is symmetric.
C) A matrix is diagonalizable if and only if it has distinct eigenvalues.
D) A matrix is diagonalizable if and only if its determinant is non-zero.
4. If A is similar to B, then A can be diagonalized if and only if B can be diagonalized.
A) True
B) False
C) Only if P is orthogonal
D) Only if A and B are symmetric
5. Which of the following is a necessary condition for a matrix A to be diagonalizable?
A) A must be symmetric.
B) The algebraic multiplicity of each eigenvalue must equal its geometric multiplicity.
C) A must have all real eigenvalues.
D) A must have a non-zero determinant.
6. If A is a non-diagonalizable matrix, what is the implication for its eigenvectors?
A) There are not enough linearly independent eigenvectors to form a basis.
B) It has no eigenvectors.
C) All its eigenvectors are linearly dependent.
D) It has only one distinct eigenvalue.
7. If A is similar to B, what is the relationship between their characteristic polynomials?
A) They are identical.
B) They are negatives of each other.
C) They are reciprocals of each other.
D) They are unrelated.
8. What is the relationship between the eigenvalues of A and the diagonal entries of D if A = PDP⁻¹?
A) The diagonal entries of D are the eigenvalues of A, in some order.
B) The diagonal entries of D are the eigenvectors of A, in some order.
C) The diagonal entries of D are the singular values of A, in some order.
D) The diagonal entries of D are the trace of A, repeated.
9. If A is a diagonalizable matrix, then A can be written as a sum of projection matrices.
A) True
B) False
C) Only if A is symmetric
D) Only if A has distinct eigenvalues
10. For a matrix A to be diagonalizable, the sum of the dimensions of its eigenspaces must equal the dimension of the vector space.
A) True
B) False
C) Only if the matrix is symmetric
D) Only if the matrix has distinct eigenvalues
11. If A is similar to B, then A and B have the same null space.
A) False
B) True
C) Only if P is the identity matrix
D) Only if A and B are diagonal
12. If A = PDP⁻¹, then P⁻¹AP = D. What is the significance of D?
A) D is a diagonal matrix containing the eigenvalues of A.
B) D is a diagonal matrix containing the eigenvectors of A.
C) D is the identity matrix.
D) D is the inverse of A.
13. If A is an n x n matrix and has n linearly independent eigenvectors, it is diagonalizable.
A) True
B) False
C) Only if the eigenvectors form an orthonormal basis
D) Only if the matrix is symmetric
14. Consider the matrix A = [[0, 1], [0, 0]]. Is this matrix diagonalizable?
A) Yes, because its only eigenvalue is 0.
B) No, because the geometric multiplicity of eigenvalue 0 is less than its algebraic multiplicity.
C) Yes, because it is similar to the zero matrix.
D) No, because its determinant is 0.
15. If A and B are similar matrices, what is the relationship between their ranks?
A) rank(A) = rank(B)
B) rank(A) = rank(B) * rank(P)
C) rank(A) = rank(B) / rank(P)
D) rank(A) = -rank(B)
16. If A = PDP⁻¹ is the diagonalization of A, and D = [[λ₁, 0], [0, λ₂]], what are the eigenvalues of A?
A) λ₁ and λ₂
B) 1/λ₁ and 1/λ₂
C) λ₁ + λ₂ and λ₁ * λ₂
D) λ₁ and 0
17. What is the condition for a matrix to be similar to a diagonal matrix D?
A) The matrix must have n distinct eigenvalues.
B) The matrix must have n linearly independent eigenvectors.
C) The matrix must be symmetric.
D) The matrix must have a non-zero determinant.
18. If A is similar to B, and B is diagonalizable, is A necessarily diagonalizable?
A) Yes
B) No
C) Only if A and B are symmetric
D) Only if P is orthogonal
19. Which of the following matrices is NOT diagonalizable?
A) [[1, 0], [0, 2]]
B) [[3, 1], [0, 3]]
C) [[4, 0], [0, 4]]
D) [[1, 1], [0, -1]]
20. If A = PDP⁻¹ is the diagonalization of A, what is P⁻¹AP equal to?
A) D
B) A
C) PDP
D) P⁻¹DP⁻¹
21. Let A be an n x n matrix. If A has n distinct eigenvalues, then it is guaranteed to be diagonalizable.
A) True
B) False
C) Only if the eigenvalues are real
D) Only if the matrix is symmetric
22. If A is similar to B, and A is invertible, is B also invertible?
A) Yes
B) No
C) Only if P is orthogonal
D) Only if A and B are diagonal
23. What does it mean for a matrix to be diagonalizable over a field F?
A) It can be transformed into a diagonal matrix using a similarity transformation with a matrix P whose entries are in F.
B) All its eigenvalues are in F.
C) It has n linearly independent eigenvectors in Fⁿ.
D) All of the above.
24. If A is a diagonalizable matrix, what can be said about its eigenspaces?
A) The sum of the dimensions of the eigenspaces equals the dimension of the vector space.
B) Each eigenspace has dimension 1.
C) The eigenspaces are orthogonal.
D) The sum of the dimensions of the eigenspaces is less than the dimension of the vector space.
25. Consider the matrix A = [[1, 0], [0, 1]]. Is this matrix diagonalizable?
A) Yes, it is already a diagonal matrix.
B) No, because its only eigenvalue is 1 with algebraic multiplicity 2.
C) Yes, but only if P is the identity matrix.
D) No, because it is not symmetric.
26. If A is similar to B, then A and B have the same characteristic polynomial.
A) True
B) False
C) Only if P is orthogonal
D) Only if A and B are diagonal
27. What is the minimal polynomial of a matrix?
A) The monic polynomial of lowest degree that annihilates the matrix.
B) The characteristic polynomial of the matrix.
C) The polynomial whose roots are the singular values of the matrix.
D) The polynomial that represents the matrix in a specific basis.
28. A matrix A is diagonalizable if and only if its minimal polynomial has no repeated roots.
A) True
B) False
C) This is true for diagonalizable matrices over algebraically closed fields.
D) This is true for symmetric matrices.
29. If A and B are similar matrices, and A has eigenvalues λ₁, λ₂, ..., λn, what are the eigenvalues of B?
A) The same eigenvalues λ₁, λ₂, ..., λn.
B) The reciprocals of the eigenvalues of A.
C) The negatives of the eigenvalues of A.
D) The eigenvalues of P⁻¹AP.
30. If A is diagonalizable, then its eigenvectors form a basis for Rⁿ (or Cⁿ).
A) True
B) False
C) Only if A is symmetric
D) Only if A has distinct eigenvalues
31. What property of a matrix guarantees that it is diagonalizable over the real numbers?
A) It is invertible.
B) It is symmetric.
C) It has only positive eigenvalues.
D) It has a non-zero trace.
32. If A = PDP⁻¹ is the diagonalization of A, what is Aᵏ equal to?
A) PDᵏP⁻¹
B) PᵏDP⁻ᵏ
C) PD⁻ᵏP⁻¹
D) P⁻¹DᵏP
33. Let A be an n x n matrix. If the geometric multiplicity of every eigenvalue of A is 1, then A is diagonalizable.
A) True
B) False
C) Only if A has n distinct eigenvalues
D) Only if A is symmetric
34. If a matrix A is similar to a diagonal matrix D, then A is diagonalizable.
A) True
B) False
C) Only if D is the identity matrix
D) Only if D has distinct diagonal entries
35. What is the characteristic polynomial of a matrix A?
A) det(A - λI)
B) det(A + λI)
C) det(λI - A)
D) det(λA - I)
36. If A and B are similar matrices, what is the relationship between their traces?
A) tr(A) = tr(B) * tr(P)
B) tr(A) = tr(B) / tr(P)
C) tr(A) = tr(B)
D) tr(A) = -tr(B)
37. Consider the matrix A = [[2, 1], [0, 2]]. Is this matrix diagonalizable?
A) Yes, because it has an eigenvalue 2 with algebraic multiplicity 2.
B) No, because the geometric multiplicity of eigenvalue 2 is less than its algebraic multiplicity.
C) Yes, because it has a non-zero determinant.
D) No, because it is not a symmetric matrix.
38. If a matrix A has n distinct eigenvalues, is it diagonalizable?
A) Yes
B) No
C) Only if it is a symmetric matrix
D) Only if it is an upper triangular matrix
39. What is the geometric multiplicity of an eigenvalue?
A) The number of times the eigenvalue appears as a root of the characteristic polynomial.
B) The dimension of the null space of (A - λI).
C) The number of distinct eigenvalues of the matrix.
D) The sum of the diagonal elements of the matrix.
40. What is the algebraic multiplicity of an eigenvalue?
A) The dimension of the eigenspace corresponding to the eigenvalue.
B) The number of linearly independent eigenvectors for the eigenvalue.
C) The number of times the eigenvalue appears as a root of the characteristic polynomial.
D) The number of distinct eigenvalues of the matrix.
41. If A is similar to B, what is the relationship between their determinants?
A) det(A) = det(B) * det(P)
B) det(A) = det(B) / det(P)
C) det(A) = det(B)
D) det(A) = -det(B)
42. A matrix is diagonalizable if and only if the algebraic multiplicity of each eigenvalue equals its geometric multiplicity.
A) True
B) False
C) This condition is necessary but not sufficient.
D) This condition is sufficient but not necessary.
43. Consider a matrix A with eigenvalues λ₁, λ₂, ..., λn. If A is diagonalizable, what are the diagonal entries of the diagonal matrix D in the expression A = PDP⁻¹?
A) The eigenvalues of A, possibly in a different order.
B) The eigenvectors of A, possibly in a different order.
C) The singular values of A, possibly in a different order.
D) The trace of A, repeated n times.
44. What is the geometric interpretation of the columns of the matrix P in the diagonalization A = PDP⁻¹?
A) They are the eigenvalues of A.
B) They are the eigenvectors of A.
C) They are the singular vectors of A.
D) They are the rows of A.
45. If matrix A is similar to matrix B, and A is diagonalizable, is B also diagonalizable?
A) Yes
B) No
C) Only if A and B are symmetric
D) Only if A and B are invertible
46. Which of the following properties is invariant under similarity transformations?
A) The sum of the diagonal elements (trace).
B) The set of eigenvalues.
C) The determinant.
D) All of the above.
47. Two matrices A and B are called similar if there exists an invertible matrix P such that B = P⁻¹AP.
A) True
B) False
C) Only if A and B are diagonal matrices
D) Only if A and B have the same determinant
48. What is the relationship between the eigenvalues of a matrix A and the diagonal entries of its diagonal form D, if A = PDP⁻¹?
A) The diagonal entries of D are the singular values of A.
B) The diagonal entries of D are the eigenvalues of A.
C) The diagonal entries of D are the trace of A.
D) The diagonal entries of D are the determinant of A.
49. If a matrix A is diagonalizable, then there exists an invertible matrix P and a diagonal matrix D such that A = PDP⁻¹.
A) True
B) False
C) Only if A is symmetric
D) Only if A has distinct eigenvalues
50. What is the primary condition for a square matrix to be diagonalizable?
A) It must have distinct eigenvalues.
B) It must have linearly independent eigenvectors equal to its dimension.
C) It must be a symmetric matrix.
D) It must have a non-zero determinant.
All Question Banks
E-Book Matrix Diagonalization and Similar Matrices One Line Questions Matrix Diagonalization and Similar Matrices Online Test Matrix Diagonalization and Similar Matrices