Math Problem Statement

You are given that the eigenvalues of a matrix A are 3, 2 and 2. Is A invertible? Your answer can be “yes”,“no” or “depends”. Give arguments and/or example to support your answer.

Solution

The answer is "yes".

A matrix AA is invertible if and only if none of its eigenvalues are zero. This is because the determinant of a matrix is the product of its eigenvalues, and a matrix is invertible if its determinant is non-zero.

In this case, the eigenvalues of AA are 3, 2, and 2. Since none of these eigenvalues is zero, the determinant of AA is non-zero. The determinant can be calculated as:

det(A)=3×2×2=12\text{det}(A) = 3 \times 2 \times 2 = 12

Since the determinant is non-zero, the matrix AA is invertible.

To summarize:

  • Eigenvalues of AA are 3, 2, and 2.
  • The determinant of AA is non-zero.
  • Therefore, AA is invertible.

Do you want any more details, or have further questions?

Here are five related questions:

  1. How is the determinant of a matrix related to its eigenvalues?
  2. What does it mean geometrically if a matrix has an eigenvalue of 0?
  3. How can you determine if a matrix is singular based on its eigenvalues?
  4. How do the eigenvalues affect the condition number of a matrix?
  5. How can you find the eigenvalues of a matrix from its characteristic equation?

Tip: The product of eigenvalues equals the determinant of a matrix, and their sum equals the trace of the matrix.

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Math Problem Analysis

Mathematical Concepts

Linear Algebra
Eigenvalues
Matrix Invertibility

Formulas

det(A) = λ1 × λ2 × λ3 (where λ1, λ2, λ3 are the eigenvalues)

Theorems

A matrix is invertible if and only if its determinant is non-zero.

Suitable Grade Level

Undergraduate Level