Eigenvalues and Eigenvectors MCQ

16. Let the eigen values of a 2 x 2 matrix A be 1, -2 with eigen vectors x1 and x2 respectively. Then the eigen values and eigen vectors of the matrix A2 – 3A + 4I would, respectively, be

  1. 2, 14; x1, x2
  2. 2, 14; x1+ x2, x1– x2
  3. 2, 0; x1, x2
  4. 2, 0; x1+ x2, x1– x2
Answer
Answer. a

17. Two eigen values of a 3 x 3 real matrix P are 2+\sqrt{-1} and 3. The determinant of P is

  1. 5
  2. 10
  3. 15
  4. 20
Answer
Answer. c

18. Consider a 2 x 2 square matrix

    \[A=\begin{bmatrix} \sigma & x\\ \omega & \sigma \end{bmatrix}\]

where x is unknown. If the eigen values of the matrix A are (σ + jω) and (σ – jω), then x is equal to

  1. + jω
  2. – jω
  3. + ω
  4. – ω
Answer
Answer. d

19. The condition for which the eigen values of the matrix A=\begin{bmatrix} 2 & 1\\ 1 & k \end{bmatrix} are positive, is

  1. k > 1/2
  2. k > -2
  3. k > 0
  4. k < -1/2
Answer
Answer. a

20. Consider a 3 x 3 matrix with every element being equal to 1. Its only non-zero eigen value is

  1. 1
  2. 2
  3. 4
  4. 3
Answer
Answer. d

21. If the entries in each column of a square matrix M add up to 1, then an eigen value of M is

  1. 4
  2. 3
  3. 2
  4. 1
Answer
Answer. d

22. Consider the following 2 x 2 matrix A where two elements are unknown and are marked by a and b. The eigen values of this matrix are -1 and 7. What are the values of a and b?

A=\begin{bmatrix} 1 & 4\\ b & a \end{bmatrix}

  1. a = 6, b = 4
  2. a = 4, b = 6
  3. a = 3, b = 5
  4. a = 5, b = 3
Answer
Answer. d

23. The value of x for which all the eigen-values of the matrix given below are real is

    \[\begin{bmatrix} 10 & 5+j & 4\\ x & 20 & 2\\ 4 & 2 & -10 \end{bmatrix}\]

  1. 5 + j
  2. 5 – j
  3. 1 – 5j
  4. 1 + 5j
Answer
Answer. b

24. At least one eigen value of a singular matrix is

  1. positive
  2. zero
  3. negative
  4. imaginary
Answer
Answer. b

25. The two eigen values of the matrix \begin{bmatrix} 2 & 1\\ 1 & p \end{bmatrix} have a ratio of 3 : 1 for p = 2. What is another value of p for which the eigen values have the same ratio of 3 : 1?

  1. -2
  2. 1
  3. 7/3
  4. 14/3
Answer
Answer. d

26. The larger of the two eigen values of the matrix \begin{bmatrix} 4 & 5\\ 2 & 1 \end{bmatrix} is

  1. 4
  2. 6
  3. 1
  4. 2
Answer
Answer. b

27. The value of p such that the vector \begin{bmatrix} 1\\ 2 \\ 3 \end{bmatrix} is an eigen vector of the matrix \begin{bmatrix} 4 & 1 & 2\\ p & 2 & 1\\ 14 & -4 & 10 \end{bmatrix} is

  1. 17
  2. 16
  3. 15
  4. 14
Answer
Answer. a

28. The lowest eigen value of the 2 x 2 matrix \begin{bmatrix} 4 & 2\\ 1 & 3 \end{bmatrix} is

  1. 5
  2. 2
  3. 3
  4. 4
Answer
Answer. b

29. The smallest and largest eigen values of the following matrix are

\begin{bmatrix} 3 & -2 & 2 \\ 4 & -4 & 6 \\ 2 & -3 & 5 \end{bmatrix}

  1. 1.5 and 2.5
  2. 0.5 and 2.5
  3. 1 and 3
  4. 1 and 2
Answer
Answer. d

30. In the given matrix \begin{bmatrix} 1 & -1 & 2\\ 0 & 1 & 0\\ 1 & 2 & 1 \end{bmatrix}, one of the eigen values is 1. The eigen vectors corresponding to the eigen value 1 are

  1. {α(4,2,1) | α ≠ 0, α ∈ R}
  2. {α(-4,2,1) | α ≠ 0, α ∈ R}
  3. {α(\sqrt{2},0,1) | α ≠ 0, α ∈ R}
  4. {α(-\sqrt{2},0,1) | α ≠ 0, α ∈ R}
Answer
Answer. b

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