1If matrix is of order and matrix is of order , then the order of matrix is:
A.
B.
C.
D.
Correct Answer:
Explanation:
When multiplying a matrix of size by a matrix of size , the inner dimensions () must match, and the resulting matrix has dimensions .
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2Which of the following is true for the transpose of the product of two matrices ?
A.
B.
C.
D.
Correct Answer:
Explanation:
The reversal rule for transposes states that .
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3A square matrix is said to be symmetric if:
A.
B.
C.
D.
Correct Answer:
Explanation:
A symmetric matrix is equal to its own transpose, i.e., for all .
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4The trace of a matrix is defined as:
A.The product of the diagonal elements
B.The sum of the principal diagonal elements
C.The sum of all elements
D.The determinant of the matrix
Correct Answer: The sum of the principal diagonal elements
Explanation:
The trace of a square matrix, denoted , is the sum of the elements on the main diagonal.
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5Which elementary row operation changes the value of the determinant of a matrix?
A.None of the above
B.Multiplying a row by 1
C.Adding a multiple of one row to another ()
D.Interchanging two rows ()
Correct Answer: Interchanging two rows ()
Explanation:
Interchanging two rows changes the sign of the determinant. Multiplying a row by a scalar multiplies the determinant by . Adding a multiple of a row to another does not change the determinant.
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6The rank of a matrix is defined as the order of the largest square sub-matrix whose determinant is:
A.Not zero
B.Positive
C.Negative
D.Zero
Correct Answer: Not zero
Explanation:
The rank is the size of the largest non-vanishing (non-zero) minor.
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7What is the rank of the identity matrix of order ?
A.$0$
B.$1$
C.
D.
Correct Answer:
Explanation:
An identity matrix is already in reduced row echelon form and has pivots, so its rank is . Its determinant is .
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8Find the rank of the matrix
A.1
B.4
C.2
D.0
Correct Answer: 1
Explanation:
The second row is $2$ times the first row (). Applying gives . Since there is only 1 non-zero row, the rank is 1.
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9If a matrix of order is singular (), then its rank is:
A.Exactly 3
B.Greater than 3
C.Less than 3
D.Exactly 0
Correct Answer: Less than 3
Explanation:
If the determinant of an matrix is zero, the matrix is not of full rank. Thus, the rank must be less than (here ).
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10The rank of a matrix is equal to:
A.The number of non-zero rows in its Echelon form
B.The number of columns
C.The sum of diagonal elements
D.The number of rows
Correct Answer: The number of non-zero rows in its Echelon form
Explanation:
The standard method to find rank is to reduce the matrix to Row Echelon Form and count the number of non-zero rows.
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11A set of vectors is linearly dependent if there exist scalars (not all zero) such that:
A.
B.
C.
D.
Correct Answer:
Explanation:
This is the definition of linear dependence. If the equation holds only when all , the vectors are linearly independent.
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12Two vectors in , and , are:
A.Linearly Independent
B.Orthogonal
C.Linearly Dependent
D.Orthonormal
Correct Answer: Linearly Dependent
Explanation:
Since , one vector is a scalar multiple of the other, making them linearly dependent. Also, the determinant .
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13If the determinant of a matrix formed by vectors as columns is non-zero, then the vectors are:
A.Parallel
B.Linearly Dependent
C.Linearly Independent
D.Zero vectors
Correct Answer: Linearly Independent
Explanation:
A non-zero determinant implies the matrix has full rank, meaning the column vectors are linearly independent.
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14What is the maximum number of linearly independent vectors in ?
A.
B.
C.
D.
Correct Answer:
Explanation:
The dimension of the vector space is . Therefore, any basis (a maximal set of linearly independent vectors) contains exactly vectors.
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15A system of linear equations is consistent if and only if:
A.
B.
C.
D.
Correct Answer:
Explanation:
This is the Rouche-Capelli theorem. The rank of the coefficient matrix must equal the rank of the augmented matrix for a solution to exist.
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16For a system of linear equations in variables , if , then the system has:
A.No solution
B.A unique solution
C.Only the trivial solution
D.Infinitely many solutions
Correct Answer: A unique solution
Explanation:
If the rank equals the number of unknowns () and the system is consistent, there is a unique solution.
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17For a system of linear equations in variables , if , then the system has:
A.No solution
B.A unique solution
C.Infinitely many solutions
D.Exactly two solutions
Correct Answer: Infinitely many solutions
Explanation:
When the rank is less than the number of variables, there are free variables, leading to infinitely many solutions.
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18The system of equations has no solution if:
A.B is a zero vector
B.
C.
D.
Correct Answer:
Explanation:
Specifically, if , the system is inconsistent and has no solution.
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19A homogeneous system of equations always has:
A.Infinite solutions
B.At least one solution (Trivial solution)
C.No solution
D.Only non-trivial solutions
Correct Answer: At least one solution (Trivial solution)
Explanation:
A homogeneous system is always consistent because is always a solution (trivial solution).
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20A homogeneous system in unknowns has a non-trivial solution if:
A.
B.A is an identity matrix
C.
D.
Correct Answer:
Explanation:
A non-trivial solution (infinite solutions) exists if the matrix is singular, meaning its rank is less than the number of variables, or .
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21Consider the system: and . This system is:
A.Consistent with infinite solutions
B.Inconsistent
C.Consistent with unique solution
D.Homogeneous
Correct Answer: Inconsistent
Explanation:
The second equation divided by 2 gives , which contradicts . Thus, no solution exists.
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22For what value of does the system , , have only the trivial solution?
A.
B.
C.
D.Any real number
Correct Answer:
Explanation:
For only a trivial solution, the determinant of the coefficient matrix must be non-zero. . Solving gives .
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23A square matrix is invertible (non-singular) if and only if:
A.
B.
C.
D.
Correct Answer:
Explanation:
The inverse exists only if the determinant is non-zero.
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24The inverse of a matrix is given by:
A.
B.
C.
D.
Correct Answer:
Explanation:
The formula for the inverse is the adjoint of the matrix divided by its determinant.
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25If and are invertible matrices, then is equal to:
A.
B.
C.
D.
Correct Answer:
Explanation:
This is the reversal law for inverses.
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26The inverse of an orthogonal matrix is:
A.
B.
C.
D.
Correct Answer:
Explanation:
By definition, an orthogonal matrix satisfies , which implies .
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27If , then is:
A.
B.
C.
D.
Correct Answer:
Explanation:
The inverse of a diagonal matrix is obtained by taking the reciprocal of the diagonal elements.
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28The roots of the characteristic equation are called:
A.Eigenvectors
B.Rank
C.Eigenvalues
D.Latent vectors
Correct Answer: Eigenvalues
Explanation:
The values of that satisfy the characteristic equation are the eigenvalues (or characteristic roots/latent roots).
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29If is an eigenvalue of and is the corresponding eigenvector, then:
A.
B.
C.
D.
Correct Answer:
Explanation:
This is the fundamental definition of an eigenvalue and eigenvector pair.
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30Find the eigenvalues of the matrix
A.1, 3
B.1, 2
C.0, 3
D.2, 3
Correct Answer: 1, 3
Explanation:
For a triangular matrix (upper or lower), the eigenvalues are simply the diagonal elements.
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31The sum of the eigenvalues of a matrix is equal to:
A.Zero
B.Trace of the matrix
C.Determinant of the matrix
D.Highest eigenvalue
Correct Answer: Trace of the matrix
Explanation:
A key property of eigenvalues is .
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32The product of the eigenvalues of a matrix is equal to:
A.1
B.Determinant of the matrix
C.Trace of the matrix
D.Rank of the matrix
Correct Answer: Determinant of the matrix
Explanation:
A key property of eigenvalues is .
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33If the eigenvalues of a matrix are 2, 3, and 4, then the eigenvalues of are:
A.2, 3, 4
B.
C.1/2, 1/3, 1/4
D.4, 9, 16
Correct Answer: 4, 9, 16
Explanation:
If is an eigenvalue of , then is an eigenvalue of .
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34If is an eigenvalue of a non-singular matrix , then the eigenvalue of is:
A.
B.
C.
D.
Correct Answer:
Explanation:
If , multiplying by gives , so .
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35The eigenvalues of a real symmetric matrix are always:
A.Real
B.0
C.Complex with non-zero imaginary part
D.Purely imaginary
Correct Answer: Real
Explanation:
A fundamental theorem of linear algebra states that all eigenvalues of a real symmetric matrix are real numbers.
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36The eigenvalues of a skew-symmetric matrix are:
A.Always real
B.Always 1
C.Always positive
D.Either 0 or purely imaginary
Correct Answer: Either 0 or purely imaginary
Explanation:
Skew-symmetric matrices have eigenvalues that are either zero or purely imaginary conjugates.
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37At least one eigenvalue of a singular matrix is:
A.-1
B.0
C.Infinite
D.1
Correct Answer: 0
Explanation:
Since the product of eigenvalues equals the determinant, and a singular matrix has determinant 0, at least one eigenvalue must be 0.
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38If has eigenvalues 2 and 5, what are the eigenvalues of ?
A.5, 8
B.2, 5
C.6, 15
D.-1, 2
Correct Answer: 5, 8
Explanation:
If is an eigenvalue of , then is an eigenvalue of . So, and .
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39What are the eigenvalues of the matrix ?
A.0, 0
B.1, -1
C.1, 1
D.-1, -1
Correct Answer: 1, -1
Explanation:
Characteristic equation: . Also, trace is 0 and determinant is -1.
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40The Cayley-Hamilton theorem states that every square matrix satisfies its own:
A.Characteristic equation
B.Inverse
C.Diagonal elements
D.Transpose
Correct Answer: Characteristic equation
Explanation:
The theorem states that if is the characteristic polynomial, then .
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41If the characteristic equation of a matrix is , then according to Cayley-Hamilton theorem:
A.
B.
C.
D.
Correct Answer:
Explanation:
Replace scalar with matrix and the constant term 6 with .
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42The Cayley-Hamilton theorem can be used to find:
A.Inverse of a matrix
B.Rank of a matrix
C.Trace only
D.Determinant only
Correct Answer: Inverse of a matrix
Explanation:
By multiplying the characteristic equation relation by , we can express as a polynomial in .
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43Given , the inverse is given by:
A.
B.
C.
D.
Correct Answer:
Explanation:
Multiply by : .
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44An eigenvector corresponding to an eigenvalue must be:
A.A column of the identity matrix
B.A non-zero vector
C.A unit vector
D.A zero vector
Correct Answer: A non-zero vector
Explanation:
By definition, an eigenvector must be a non-zero vector. If , holds for any , which is trivial.
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45Algebraic Multiplicity of an eigenvalue refers to:
A.The rank of the matrix
B.The number of linearly independent eigenvectors associated with it
C.The number of times the eigenvalue appears as a root of the characteristic equation
D.The value of the eigenvalue itself
Correct Answer: The number of times the eigenvalue appears as a root of the characteristic equation
Explanation:
This is the definition of Algebraic Multiplicity. The number of independent eigenvectors is the Geometric Multiplicity.
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46A square matrix of order is diagonalizable if and only if:
A.It is symmetric
B.Its determinant is non-zero
C.It has distinct eigenvalues
D.It has linearly independent eigenvectors
Correct Answer: It has linearly independent eigenvectors
Explanation:
Having independent eigenvectors allows us to form the matrix such that is diagonal. Distinct eigenvalues is a sufficient but not necessary condition (repeated eigenvalues can still have independent eigenvectors).
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47If , its eigenvalues are:
A.0, 0
B.1, 0
C.1, 1
D.-1, -1
Correct Answer: 1, 1
Explanation:
is the identity matrix. Its eigenvalues are the diagonal entries, which are 1 and 1.
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48Which of the following matrices is in Row Echelon Form?
A.
B.
C.
D.
Correct Answer:
Explanation:
In Row Echelon Form, all non-zero rows are above any rows of all zeros, and the leading coefficient of a non-zero row is always strictly to the right of the leading coefficient of the row above it.
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49If is a matrix with eigenvalues 1, -1, and 2, the determinant of is:
A.2
B.-2
C.3
D.0
Correct Answer: -2
Explanation:
Determinant = Product of eigenvalues = .
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50If is a matrix with eigenvalues 1, -1, and 2, the Trace of is: