Math Problem Statement

Tìm ma trận nghịch đảo của ma trận A = \begin{pmatrix} 1 & 1 & -1 \\ 1 & 3 & 1 \\ 2 & 2 & -1 \end{pmatrix}

Solution

The problem asks to find the inverse of matrix A=(111131221)A = \begin{pmatrix} 1 & 1 & -1 \\ 1 & 3 & 1 \\ 2 & 2 & -1 \end{pmatrix}.

To find the inverse of a 3x3 matrix, follow these steps:

  1. Calculate the determinant of matrix AA: det(A)=1312111121+(1)1322\text{det}(A) = 1 \cdot \begin{vmatrix} 3 & 1 \\ 2 & -1 \end{vmatrix} - 1 \cdot \begin{vmatrix} 1 & 1 \\ 2 & -1 \end{vmatrix} + (-1) \cdot \begin{vmatrix} 1 & 3 \\ 2 & 2 \end{vmatrix} We will evaluate each of these 2x2 determinants.

  2. Cofactor expansion and adjugate matrix: After finding the determinant, we compute the cofactors for each element of matrix AA to construct the adjugate matrix.

  3. Divide adjugate matrix by the determinant: If the determinant is non-zero, the inverse is given by: A1=1det(A)×adj(A)A^{-1} = \frac{1}{\text{det}(A)} \times \text{adj}(A)

Let me compute the detailed solution for you now.The determinant of matrix AA is det(A)=2.0\text{det}(A) = 2.0, which is non-zero, so the inverse exists.

The inverse of matrix AA is:

-2.5 & -0.5 & 2 \\ 1.5 & 0.5 & -1 \\ -2 & 0 & 1 \end{pmatrix}$$ Would you like more details on how the inverse was calculated, or do you have any other questions? Here are 5 related questions to expand on this: 1. How is the determinant of a matrix calculated? 2. What does it mean when the determinant of a matrix is zero? 3. How is the adjugate matrix related to the inverse? 4. Can every square matrix have an inverse? 5. What are the properties of an inverse matrix? **Tip**: The inverse of a matrix is used in solving systems of linear equations, especially when dealing with matrix equations of the form $$A\mathbf{x} = \mathbf{b}$$.

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Math Problem Analysis

Mathematical Concepts

Matrix Algebra
Inverse of a Matrix
Determinants
Adjugate Matrix

Formulas

Inverse of a matrix: A^{-1} = \frac{1}{\text{det}(A)} \times \text{adj}(A)
Determinant of a 3x3 matrix: \text{det}(A) = a(ei − fh) − b(di − fg) + c(dh − eg)

Theorems

Properties of the inverse of a matrix
Cramer's rule for finding inverses

Suitable Grade Level

College or Advanced High School