Enough Work - 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: Enough Work, Vector, Matrix, Find Matrices, Equation, Simplify, Data Points, Least Squares, Best Fits, Values

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2012/2013

Uploaded on 02/27/2013

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NAME:
Math 205 - Final Exam - April 10, 2006
Instructions: Show enough work to justify your final answers.
1. (14 pts.) Let y=
1
3
5
,u1=
1
3
2
,u2=
5
1
4
, and let W=Span{u1,u2}.
(a) Is yin W?
(b) Find the vector in Wthat is closest to y.
(c) Find a vector in W.
pf3
pf4
pf5

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NAME:

Math 205 - Final Exam - April 10, 2006

Instructions: Show enough work to justify your final answers.

  1. (14 pts.) Let y =

, u 1 =

, u 2 =

, and let W =Span{u 1 , u 2 }.

(a) Is y in W?

(b) Find the vector in W that is closest to y.

(c) Find a vector in W ⊥.

  1. (14 pts.) Consider the matrix A =

[

]

(a) Show that A is diagonalizable. That is, find matrices P and D and write the equation involving A, P , and D.

(b) Using your result in part (a), simplify Ak. (Your answer should be a single matrix.)

  1. (12 pts.) Suppose A is a 4 × 4 matrix with eigenvalues -3, 0, and 2. Assume that the eigenspace of λ = 2 is 2-dimensional.

(a) Is A invertible? Why or why not?

(b) Is A diagonalizable? Why or why not?

(c) Suppose u and v are in the eigenspace of λ = −3. Is it possible that u and v are linearly independent?

(d) Suppose w is in the eigenspace of λ = 2. Calculate A^5 w.

  1. (6 pts.) Suppose that λ is a non-zero eigenvalue of an invertible matrix A. Show that 1/λ is an eigenvalue of A−^1. (Hint: Consider the equation Ax = λx.)
  1. (14 pts.) Consider the quadratic form Q(x) = xT^ Ax, where A =

The eigenvalues are 5, 2, and -1, with corresponding eigenvectors

, and

(a) Write out Q(x) in terms of x 1 , x 2 , and x 3.

(b) Find a matrix P such that the change of variables x = P y transforms the quadratic form into one with no cross-product term.

(c) Write the new quadratic form with no cross-product term.

(d) Bonus: Find a vector x such that Q(x) is negative.

  1. (12 pts.) Consider the linear transformation T : R^2 → R^2 where T (x) reflects points about the line x 2 = x 1. Let A be the standard matrix of the transformation T. (a) Find two linearly independent eigenvectors of A, and give their corresponding eigenvalues.

(b) Is T a one-to-one transformation? Explain.

(c) Is T an onto transformation? Explain.

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