Math Problem Statement

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Find a diagonal matrix D and an invertible matrix P such that A = PDP^{-1} for A = \begin{bmatrix} 5 & 1 & -1 \\ 2 & 4 & -2 \\ 1 & -1 & 3 \end{bmatrix}. Assume that A has eigenvalues \lambda_1 = 2, \lambda_2 = 4, and \lambda_3 = 6.

Solution

This solution involves finding matrices DD and PP for the matrix AA, such that A=PDP1A = P D P^{-1}, where AA is given and has eigenvalues λ1=2\lambda_1 = 2, λ2=4\lambda_2 = 4, and λ3=6\lambda_3 = 6.

The steps in the solution involve:

  1. Finding Eigenvectors for Each Eigenvalue:

    • For λ1=2\lambda_1 = 2, the matrix (A2I)(A - 2I) is created and row-reduced to find the eigenvector associated with λ1\lambda_1.
    • For λ2=4\lambda_2 = 4, the matrix (A4I)(A - 4I) is created, row-reduced, and its eigenvector is found.
    • For λ3=6\lambda_3 = 6, the matrix (A6I)(A - 6I) is similarly handled to determine its eigenvector.
  2. Constructing PP and DD:

    • PP is formed by placing each eigenvector as columns, corresponding to λ1\lambda_1, λ2\lambda_2, and λ3\lambda_3.
    • DD is constructed as a diagonal matrix with eigenvalues λ1\lambda_1, λ2\lambda_2, and λ3\lambda_3 on the diagonal.

The final matrices obtained are:

  • P=[101110110]P = \begin{bmatrix} 1 & 0 & 1 \\ 1 & 1 & 0 \\ 1 & -1 & 0 \end{bmatrix}
  • D=[200040006]D = \begin{bmatrix} 2 & 0 & 0 \\ 0 & 4 & 0 \\ 0 & 0 & 6 \end{bmatrix}

Would you like a detailed breakdown of each step or have specific questions?

Related Questions

  1. How can I verify that A=PDP1A = P D P^{-1} holds for these matrices?
  2. What are some properties of diagonalizable matrices?
  3. How are eigenvalues and eigenvectors calculated for larger matrices?
  4. How does the choice of basis affect the diagonalization process?
  5. Can all matrices be diagonalized, and why or why not?

Tip: When constructing PP from eigenvectors, ensure they are linearly independent for PP to be invertible.

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Matrix Diagonalization
Eigenvalues and Eigenvectors

Formulas

A = PDP^{-1}
(A - \lambda I)\vec{x} = 0

Theorems

Diagonalization Theorem

Suitable Grade Level

College Level (Linear Algebra)