MTH007 LINEAR ALGEBRA Sample exam paper
Hello, dear friend, you can consult us at any time if you have any questions, add WeChat: daixieit
MTH007
Sample exam paper
BACHELOR DEGREE - Year 1
LINEAR ALGEBRA
Part I: True or False (3 marks for each question, 30 marks in total).
Answer True or False for each of the questions from 1 to 10. No justification is needed.
Question 1. If the matrices A and B satisfying AB = BA, then A and B must be square matrix of same size.
Question 2. If A and B are two nonsingular matrices of the same size, then A + B must be nonsingular and (A + B) − 1 = A − 1 + B − 1 .
Question 3. Let v1 , v2 and v3 are linearly dependent vectors, then v1 must be expressible as a linear combination of v2 and v3 .
Question 4. The solution set of a non-homogeneous system Ax = b can be expressed as the sum of a particular solution of this system Ax = b and the general solution of Ax = 0.
Question 5. Let A be an n × n, n > 3 matrix, then det(2A) = 2det(A).
Question 6. The set of vectors consisting of v1 , v2 , v3 and v4 is linearly independent, where
┌ 1┐ ┌ 2┐ ┌ 1┐ ┌ 1┐
v1 = ''1(1)│' , v2 = ''0(1)│' , v3 = ''0(2)│' , v4 = ''0(1)│' .
Question 7. If B is obtained from a matrix A by several elementary row operations, then rank(B) = rank(A). Question 8. The dimension of the column space of a matrix A equals to the dimension of its null space . Question 9. Let A be an m × n matrix. If there exists an n × m matrix C such that CA = I| , then m > n. Question 10. If λ is an eigenvalue of the square matrix A, then λ2 + 2 must be the eigenvalue of A2 + 2I .
Part II: Multiple Choice questions (3 marks for each question, 30 marks in total)
Please choose the best answer for each of the following questions.
Question 11.Which of the following matrices is a reduced echelon matrix? Answer
A. ┐│; B. ┐│; C. ┐│; ' 0 0 -2 1 ' ' 0 0 -2 1 ' ' 0 0 -2 1 '
┌ 0 D. ' -1 ' -1 |
1 1 1 -1 0 -2 |
1(1) ┐│; 1 ' |
┌ 1 E. ' 0 ' 0 |
0 1 0 |
2 1 0 |
0(0) ┐│ 1 '. |
Question 12. Which of the following homogeneous system of linear equations has nontrivial solutions ?
Answer
| 3x1 + 5x2 - 4x3 = 0 |
| |
3x1 + 5x2 - 4x3 = 0 |
|
6x1 + x2 - x3 = 0
3x1 + 5x2 - 4x3 = 0 |
|
|
3x1 + 5x2 - 4x3 = 0 -3x1 - 2x2 + 4x3 = 0 . 6x1 + x2 - 3x3 = 0
E. None of the above.
Question 13. Let
┌ 1 ┐ ┌ 5 ┐ ┌ -3 ┐
v1 = '' -(-)2(1) │' , v2 = '' -(-)7(4) │' , v3 = '' 0(1) '
For what value of α will the vector ϕ be in Span{v1 , v2 , v3 } ?
Answer
┌ -4 ┐
and ϕ = ' 3 │
A. 1; B. 5; C. 10; D. 0. E. None of the answers above.
Question 14. Given the n × n matrix A, B and C, Which of the following statement is NOT always true ? Answer
A. A + B = B + A;
B. (A + B)T = AT + BT ;
C. A(B + C) = AB + AC;
D. AB = BA;
E. None of the answers above, i.e. all the answers above are correct.
Question 15. Let A and B be nonsingular square matrices of the same size. Which of the following statement is NOT always true ? Answer
A. det((AB)T ) = det(AB);
B. det(AB) = det(A)det(B);
C. det(A + B) = det(A) + det(B);
D. det((AB) − 1 ) = ;
E. None of the answers above, i. e. all the statements above are true.
Question 16. Suppose
│ │ = 7.
Which of the following determinant is not 7? Answer
A. │ a d b e c f │; B. 6(1) │ 2 d 2b e 2c f │; C. │ │;
D. │ a 2d b 2e c 2f │; E. │ a 2d b 2e c 2f │ .
Question 17 Which of the following statement is NOT always true ? Answer
A. If A is an m × n matrix and the equation Ax = b is consistent for some b, then the columns of A span Rm .
B. If linear system Ax = b has distinct solutions, then so does the linear system Ax = 0.
C. If A is an m × n matrix, and Ax = b has distinct solutions. If Ax = c is consistent, then the linear system Ax = c has distinct solutions.
D. If A is a nonsingular matrix, then columns of A are linearly independent.
E. None of the answers above, i.e. all the statements above are true.
Question 18. Which of the following statement is NOT always true ? Answer
A. If A is a square matrix and the equation Ax = 0 has only the trivial solution, then A is row equivalent to the n × n identity matrix.
B. If the equation Ax = b has more than one solution, then Ax = 0 has infinite many solutions.
C. If A is an n × n matrix, then the equation Ax = b has at least one solution for each b e R| .
D. If AT is not invertible, then A must be not invertible.
E. If A and B are n × n nonsingular matrices, then AB is invertible.
Question 19. Determine the value of c such that the vectors v1 , v2 and v3 are linearly dependent, where
v1 = ┌'1(c)┐│ ┌'c(1)┐│ ┌'1(1)┐│
Answer
A. c = 1;
B. c = -2;
C. c = 1 or c = -2;
D. c = -1 or c = 2;
E. None of the answers above
Question 20.
Find all the values of a and b such that the following linear system has no solution?
| ax1 + x2 + x3 = 4
x1 + bx2 + x3 = 3
│ x1 + 2bx2 + x3 = 4
Answer
A. a = 1;
B. b = 0;
C. a = 1 or b = 0;
D. a = 1 and b , or b = 0;
E. None of the answers above
Part III: Blank filling questions (3 marks for each question, 18 marks in total)
Question 21. Given the matrix A = ┐ and B = ┌'' -121┐│', then A + BT = .
Question 22. Let u = ┌''2(1) ┐│' and v = ┌'' 4(1) ┐│'. Then (uvT )10 = .
| 2x1 - x2 - x3 = 4
Question 23. Solve the linear system and find the solution 3x1 + 4x2 - 2x3 = 11
│ 3x1 - 2x2 + 4x3 = 11
The solution is x = .
Question 24. Given A = ┐│
3 2 1
Question 25. Consider the matrix ┌ 3 ' 1 A = ' ' 1 ' |
1 3 1 1 |
1 1 3 1 |
┐│││ . ' |
Then the determinant of matrix A: det(A) = .
Question 26. Find the dimension of the vector space spanned by the vectors v1 , v2 and v3 ,
where v1 = ┌'''12-1┐│││, v2 = ┌'''1┐│││, v3 = ┌'''--24(2)┐│││ .
' ' ' ' ' '
Answer .
Part IV: Comprehensive Questions (11 marks for each question, 22 marks in total)
Please write down your solutions with detailed justifications.
Question 27. (11 marks)
Consider the matrix
A = ┐│
' 3 4 5 6 ' .
1. Find the reduced echelon form for the matrix A.
2. Find a basis for N(A) (the null space of A) and the dimension of N(A).
3. Find the dimension of the column space of A and the row space of A.
4. Give a reason why the dimension of the row space equals to the dimension of the column space.
Question 28. (11 marks)
Given the vectors v1 = ┌'2(3) ┐│ ┌' -01 ┐│ ┌' -(-)2(2) ┐│ and let A = [v1 v2 v3].
1. Prove that the two vectors v1 and v2 are linearly independent.
2. Prove that the matrix A is singular (not invertible).
3. Find all the eigenvalues and the corresponding eigenvectors for each eigenvalue.
4. Prove that the any two eigenvectors belonging to distinct eigenvalues are linearly independent for a square matrix A.
5. Prove that the any three eigenvectors belonging to distinct eigenvalues are linearly independent for a square matrix A.
2022-12-14