Matrices - characteristic roots, Cayley–Hamilton theorem, canonical forms under equivalence - Question Bank

1. The characteristic roots of A and A⁻¹ (if A is invertible) are:
A) Reciprocals of each other
B) The same
C) Opposite
D) Unrelated
2. The characteristic roots of A and A^T are:
A) The same
B) Opposite
C) Reciprocal
D) Unrelated
3. The set of all matrices similar to a given matrix A forms a:
A) Class
B) Group
C) Ring
D) Field
4. The set of all matrices equivalent to a given matrix A forms a:
A) Class
B) Group
C) Ring
D) Field
5. If a matrix A is similar to a diagonal matrix D, then A is called:
A) Diagonalizable
B) Equipotent
C) Orthogonal
D) Normal
6. The canonical form of a matrix under equivalence is determined by its:
A) Invariant factors
B) Eigenvalues
C) Minimal polynomial
D) Characteristic polynomial
7. According to the Cayley-Hamilton theorem, for A = [[2, 1], [1, 2]], we have:
A) A² - 4A + 3I = 0
B) A² + 4A + 3I = 0
C) A² - 3A + 4I = 0
D) A² + 3A + 4I = 0
8. The eigenvalues of A = [[2, 1], [1, 2]] are:
A) 1 and 3
B) 2 and 2
C) -1 and 3
D) 1 and 1
9. If A = [[2, 1], [1, 2]], its characteristic equation is:
A) λ² - 4λ + 3 = 0
B) λ² + 4λ + 3 = 0
C) λ² - 3λ + 4 = 0
D) λ² + 3λ + 4 = 0
10. The Cayley-Hamilton theorem can be used to:
A) Find the inverse of a matrix
B) Find the determinant of a matrix
C) Find the eigenvalues of a matrix
D) All of the above
11. If A is a singular matrix, then at least one of its eigenvalues is:
A) 0
B) 1
C) Non-zero
D) Complex
12. The characteristic equation of a 2x2 matrix [[a, b], [c, d]] is:
A) λ² - (a+d)λ + (ad-bc) = 0
B) λ² + (a+d)λ + (ad-bc) = 0
C) λ² - (a+d)λ - (ad-bc) = 0
D) λ² + (a+d)λ - (ad-bc) = 0
13. If A and B are equivalent matrices, they have the same:
A) Rank
B) Determinant
C) Trace
D) Eigenvalues
14. The canonical form under congruence transformation for a real symmetric matrix is:
A) A diagonal matrix with +1, -1, and 0 on the diagonal
B) A diagonal matrix with eigenvalues on the diagonal
C) Jordan Normal Form
D) Smith Normal Form
15. The Jordan Normal Form is a canonical form under which transformation?
A) Similarity
B) Equivalence
C) Congruence
D) Unitary equivalence
16. A matrix A is diagonalizable if and only if:
A) Its minimal polynomial has distinct roots
B) Its characteristic polynomial has distinct roots
C) Its determinant is non-zero
D) Its trace is non-zero
17. If A is a nilpotent matrix, then all its eigenvalues are:
A) Zero
B) One
C) Real
D) Imaginary
18. The characteristic polynomial of a 3x3 matrix A is given by -λ³ + tr(A)λ² - (sum of principal minors of order 2)λ + det(A). This is consistent with:
A) The properties of eigenvalues and the characteristic equation
B) The Cayley-Hamilton theorem
C) Smith Normal Form
D) Jordan Normal Form
19. Which of the following is NOT preserved under equivalence transformations?
A) Rank
B) Determinant
C) Trace
D) Eigenvalues
20. Which of the following is NOT preserved under similarity transformations?
A) Eigenvalues
B) Determinant
C) Trace
D) Rank
21. The canonical form under similarity is obtained by applying:
A) Similarity transformations
B) Elementary row and column operations
C) Orthogonal transformations
D) Unitary transformations
22. The canonical form under equivalence is obtained by applying:
A) Elementary row and column operations
B) Similarity transformations
C) Orthogonal transformations
D) Unitary transformations
23. If A is an orthogonal matrix, its eigenvalues have absolute value:
A) 1
B) 0
C) Greater than 1
D) Less than 1
24. If A is a skew-symmetric matrix with real entries, its eigenvalues are:
A) Purely imaginary or zero
B) Real
C) Complex
D) Positive
25. If A is a real symmetric matrix, its eigenvalues are:
A) Real
B) Complex
C) Imaginary
D) Zero
26. The set of all eigenvalues of a matrix A is called its:
A) Spectrum
B) Characteristic set
C) Eigen-set
D) Root set
27. If A is an n x n matrix, and λ1, λ2, ..., λn are its eigenvalues (counting multiplicity), then tr(A) = Σ(λi) and det(A) = Π(λi). This is a consequence of:
A) The properties of characteristic roots
B) The Cayley-Hamilton theorem
C) The definition of equivalence
D) The definition of similarity
28. According to the Cayley-Hamilton theorem, the characteristic polynomial p(λ) = det(A - λI) satisfies:
A) p(A) = 0
B) p(A) = I
C) p(A) = A
D) p(A) = det(A)
29. What is the minimum polynomial of a matrix A?
A) The monic polynomial of least degree that annihilates A
B) The characteristic polynomial of A
C) The polynomial whose roots are the eigenvalues of A
D) The polynomial of degree 1 that annihilates A
30. If A is a diagonal matrix, its eigenvalues are:
A) The diagonal entries
B) The off-diagonal entries
C) Zero
D) One
31. The characteristic roots of a matrix are also known as:
A) Eigenvalues
B) Latent roots
C) Principal values
D) All of the above
32. Two matrices A and B are similar if there exists an invertible matrix P such that:
A) B = P⁻¹AP
B) B = PAP⁻¹
C) B = P⁻¹PA
D) B = AP⁻¹P
33. If two matrices are similar, they have the same:
A) Eigenvalues
B) Determinant
C) Trace
D) All of the above
34. The canonical form under similarity transformation is:
A) Jordan Normal Form
B) Smith Normal Form
C) Row Echelon Form
D) Reduced Row Echelon Form
35. The invariant factors of a matrix are:
A) Unique polynomials that are preserved under elementary row and column operations
B) The eigenvalues of the matrix
C) The eigenvectors of the matrix
D) The entries of the matrix
36. Two matrices A and B are equivalent if there exists an invertible matrix P such that:
A) B = P⁻¹AP
B) B = PAP⁻¹
C) B = P⁻¹PA
D) B = AP⁻¹P
37. What is the Smith Normal Form of a matrix?
A) A diagonal matrix with invariant factors on the diagonal
B) A matrix with all ones on the diagonal
C) A matrix similar to the original matrix
D) A matrix derived from row and column operations
38. The canonical form of a matrix under equivalence transformation is unique if the matrix is:
A) In Smith Normal Form
B) Diagonalizable
C) Symmetric
D) Hermitian
39. If A is a 2x2 matrix with eigenvalues λ1 and λ2, then det(A) is equal to:
A) λ1 * λ2
B) λ1 + λ2
C) λ1 - λ2
D) (λ1 + λ2) / 2
40. If A is a 2x2 matrix with eigenvalues λ1 and λ2, then tr(A) is equal to:
A) λ1 + λ2
B) λ1 * λ2
C) λ1 - λ2
D) (λ1 + λ2) / 2
41. Which theorem guarantees that a matrix is a root of its characteristic polynomial?
A) Cayley-Hamilton theorem
B) Schur's theorem
C) Perron-Frobenius theorem
D) Spectral theorem
42. For an n x n matrix A, how many eigenvalues can it have?
A) At most n
B) Exactly n
C) Exactly n^2
D) At least n
43. The scalar λ in the equation Av = λv is called the:
A) Eigenvalue
B) Eigenvector
C) Characteristic root
D) Scalar multiplier
44. What is an eigenvector of a matrix A?
A) A non-zero vector v such that Av = λv for some scalar λ
B) A vector v such that Av = 0
C) A vector v such that v^T A = 0
D) A vector v such that Av = v
45. If A is an n x n matrix, its characteristic polynomial has a degree of:
A) n
B) n-1
C) n+1
D) 1
46. What is the determinant of a matrix A if λ = 0 is one of its eigenvalues?
A) 0
B) 1
C) The product of non-zero eigenvalues
D) The sum of eigenvalues
47. What is the trace of a square matrix?
A) The sum of its diagonal elements
B) The product of its diagonal elements
C) The determinant of the matrix
D) The sum of all its elements
48. If A is a square matrix, what does the Cayley-Hamilton theorem state about A?
A) A satisfies its characteristic polynomial, i.e., p(A) = 0
B) A is always diagonalizable
C) The determinant of A is always zero
D) The trace of A is always zero
49. According to the Cayley-Hamilton theorem, every square matrix satisfies its own:
A) Characteristic equation
B) Minimal polynomial
C) Eigenvector equation
D) Eigenvalue equation
50. The roots of the characteristic equation of a matrix are called:
A) Eigenvalues
B) Singular values
C) Roots of unity
D) Determinants