If L and U are invertible, then (LU)²001-U001L001 Find A001 from the given LU factorization: = -2 0 0 -2 0 0 18 -2 6 0 -7 A = LU A = -1 -2 7 7 H 1 -9 -3 0 1 -7 ][ 1 0 0 -1

Advanced Engineering Mathematics
10th Edition
ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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### Understanding Invertibility and LU Factorization

#### Problem Statement:
Given the matrices \( L \) and \( U \) are invertible, the equation \( (LU)^{-1} = U^{-1}L^{-1} \) holds true. The goal is to find \( A^{-1} \) from the given LU factorization.

Given Matrix:
\[ A = LU = \begin{bmatrix} -2 & 0 & 0 \\ 18 & -1 & -2 \\ 6 & 7 & 7 \end{bmatrix} = \begin{bmatrix} 1 & 0 & 0 \\ -9 & 1 & 0 \\ -3 & -7 & 1 \end{bmatrix} \begin{bmatrix} -2 & 0 & 0 \\ 0 & -1 & -2 \\ 0 & 0 & -7 \end{bmatrix} \]

#### Task:
Find the inverse of matrix \( A \), denoted as \( A^{-1} \), using the given LU factorization.

#### Matrix Definitions:
- **L (Lower Triangular Matrix):**
  \[ 
  L = \begin{bmatrix} 
  1 & 0 & 0 \\ 
  -9 & 1 & 0 \\ 
  -3 & -7 & 1 
  \end{bmatrix} 
  \]

- **U (Upper Triangular Matrix):**
  \[ 
  U = \begin{bmatrix} 
  -2 & 0 & 0 \\ 
  0 & -1 & -2 \\ 
  0 & 0 & -7 
  \end{bmatrix} 
  \]

To find \( A^{-1} \):
\[ 
A^{-1} = (LU)^{-1} = U^{-1}L^{-1} 
\]

#### Steps:
1. **Compute \( U^{-1} \):**  
   Find the inverse of the upper triangular matrix \( U \).

2. **Compute \( L^{-1} \):**  
   Find the inverse of the lower triangular matrix \( L \).

3. **Multiply \( U^{-1} \) and \( L^{-1} \):**  
   Multiply the results of \( U^{-1} \) and \( L^{-1} \) to obtain \( A^{-1
Transcribed Image Text:### Understanding Invertibility and LU Factorization #### Problem Statement: Given the matrices \( L \) and \( U \) are invertible, the equation \( (LU)^{-1} = U^{-1}L^{-1} \) holds true. The goal is to find \( A^{-1} \) from the given LU factorization. Given Matrix: \[ A = LU = \begin{bmatrix} -2 & 0 & 0 \\ 18 & -1 & -2 \\ 6 & 7 & 7 \end{bmatrix} = \begin{bmatrix} 1 & 0 & 0 \\ -9 & 1 & 0 \\ -3 & -7 & 1 \end{bmatrix} \begin{bmatrix} -2 & 0 & 0 \\ 0 & -1 & -2 \\ 0 & 0 & -7 \end{bmatrix} \] #### Task: Find the inverse of matrix \( A \), denoted as \( A^{-1} \), using the given LU factorization. #### Matrix Definitions: - **L (Lower Triangular Matrix):** \[ L = \begin{bmatrix} 1 & 0 & 0 \\ -9 & 1 & 0 \\ -3 & -7 & 1 \end{bmatrix} \] - **U (Upper Triangular Matrix):** \[ U = \begin{bmatrix} -2 & 0 & 0 \\ 0 & -1 & -2 \\ 0 & 0 & -7 \end{bmatrix} \] To find \( A^{-1} \): \[ A^{-1} = (LU)^{-1} = U^{-1}L^{-1} \] #### Steps: 1. **Compute \( U^{-1} \):** Find the inverse of the upper triangular matrix \( U \). 2. **Compute \( L^{-1} \):** Find the inverse of the lower triangular matrix \( L \). 3. **Multiply \( U^{-1} \) and \( L^{-1} \):** Multiply the results of \( U^{-1} \) and \( L^{-1} \) to obtain \( A^{-1
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