Interchanging Rows - Linear Algebra - Exam, Exams of Linear Algebra

This is the Exam of Linear Algebra which includes Largest Possible Rank, Matrix, Smallest, Possible Dimension, Matrix, Distance, Vector, Linear Transformation, Matrix etc. Key important points are: Interchanging Rows, Determinants, Properties, Obtained, Invertible, Basis, Dimension, Sets, Appropriate, Vector Space

Typology: Exams

2012/2013

Uploaded on 02/27/2013

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Math 205B Test 2 (45 points)
Name:
Check that you have 6 questions on three pages.
Show all your work to receive full credit for a problem.
1. (8 points) Let Aand Bbe 3 ×3 matrices, with det A= 2 and det B=5. Use properties
of determinants to compute:
(a) det 4B
(b) det Cwhere Cis obtained from Aby interchanging rows 1 and 3
(c) det ATBT
(d) det (AB )1if AB is invertible. Otherwise, explain why AB is not invertible.
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Math 205B Test 2 (45 points)

Name:

  • Check that you have 6 questions on three pages.
  • Show all your work to receive full credit for a problem.
  1. (8 points) Let A and B be 3 × 3 matrices, with det A = 2 and det B = −5. Use properties of determinants to compute:

(a) det 4B

(b) det C where C is obtained from A by interchanging rows 1 and 3

(c) det AT^ BT

(d) det (AB)−^1 if AB is invertible. Otherwise, explain why AB is not invertible.

  1. (6 points) Determine if each of the following sets is a subspace of the appropriate vector space. If so, find a basis and dimension of the subspace.

(a) Let W =

a − b + 2c 2 b + 2c + d 4 b + 4c + 2d a + b + 4c + d

 :^ a, b, c, d^ are real numbers.

. Is W a subspace of R^4?

Explain.

(b) Let W =

a + b b − 2 b + 1

 (^) : a, b are real numbers.

. Is W a subspace of R^3? Explain.

  1. (a) (5 points) Find the characteristic polynomial of the matrix

[

]

and then find all the eigenvalues by solving the charateristic equation.

(b) (3 points) The vector

[

]

is an eigenvector of the matrix

[

]

. Find the corresponding eigenvalue.

(c) (4 points) Find a non-zero vector in Nul A where A =

(d) (3 points) Let ~b 1 =

, ~b 2 =

, and ~b 3 =

 (^) be vectors in R^3. Then

B = {~b 1 ,~b 2 ,~b 3 } is a basis for R^3. If [~x]B =

, then find ~x.