Solve the linear system Ax = b by finding an LU-factorization of the coefficient matrix A, solving the lower triangular system Ly = b, and solving the upper triangular system Ux = y. 2x + y 1 %3! y - z = -2x + y + z = -2 (a) Find an LU-factorization of the coefficient matrix A. (Your L matrix must be unit diagonal.) LU = (b) Solve the lower triangular system Ly = b. y = (c) Solve the upper triangular system Ux = y. X = D00

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Chapter2: Second-order Linear Odes
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### Solving Linear Systems Using LU Factorization

#### Problem Statement
Solve the linear system \( \mathbf{A}\mathbf{x} = \mathbf{b} \) by finding an \( LU \)-factorization of the coefficient matrix \(\mathbf{A}\), solving the lower triangular system \( \mathbf{L}\mathbf{y} = \mathbf{b} \), and solving the upper triangular system \( \mathbf{U}\mathbf{x} = \mathbf{y} \).

Given system:
\[ 
\begin{aligned}
2x + y &= 1 \\
y - z &= 2 \\
-2x + y + z &= -2 \\
\end{aligned}
\]

#### Steps to Solve

**(a) Find an \( LU \)-factorization of the coefficient matrix \(\mathbf{A}\).**
    
    Your \( \mathbf{L} \) matrix must be unit diagonal.

The process involves decomposing matrix \(\mathbf{A}\) into a lower triangular matrix \(\mathbf{L}\) and an upper triangular matrix \(\mathbf{U}\).

\[
LU = 
\begin{bmatrix}
 &  &  \\
 &  &  \\
 &  &  
\end{bmatrix}
\rightarrow
\begin{bmatrix}
 &  &  \\
 &  &  \\
 &  &  
\end{bmatrix}
\rightarrow
\begin{bmatrix}
 &  &  \\
 &  &  \\
 &  &  
\end{bmatrix}
\]

**(b) Solve the lower triangular system \( \mathbf{L}\mathbf{y} = \mathbf{b} \).**
    
\[
y = 
\begin{bmatrix}
 \\
 \\
 
\end{bmatrix}
\rightarrow
\]

**(c) Solve the upper triangular system \( \mathbf{U}\mathbf{x} = \mathbf{y} \).**
    
\[
x = 
\begin{bmatrix}
 \\
 \\
 
\end{bmatrix}
\rightarrow
\]

### Diagram Explanation

1. **LU Decomposition:**
   - **Matrix \(\mathbf{L}\)**: A 3x3 lower triangular matrix with a unit diagonal (diagonal elements are 1).
   - **Matrix \(\mathbf{U}\)**: A 3x3 upper
Transcribed Image Text:### Solving Linear Systems Using LU Factorization #### Problem Statement Solve the linear system \( \mathbf{A}\mathbf{x} = \mathbf{b} \) by finding an \( LU \)-factorization of the coefficient matrix \(\mathbf{A}\), solving the lower triangular system \( \mathbf{L}\mathbf{y} = \mathbf{b} \), and solving the upper triangular system \( \mathbf{U}\mathbf{x} = \mathbf{y} \). Given system: \[ \begin{aligned} 2x + y &= 1 \\ y - z &= 2 \\ -2x + y + z &= -2 \\ \end{aligned} \] #### Steps to Solve **(a) Find an \( LU \)-factorization of the coefficient matrix \(\mathbf{A}\).** Your \( \mathbf{L} \) matrix must be unit diagonal. The process involves decomposing matrix \(\mathbf{A}\) into a lower triangular matrix \(\mathbf{L}\) and an upper triangular matrix \(\mathbf{U}\). \[ LU = \begin{bmatrix} & & \\ & & \\ & & \end{bmatrix} \rightarrow \begin{bmatrix} & & \\ & & \\ & & \end{bmatrix} \rightarrow \begin{bmatrix} & & \\ & & \\ & & \end{bmatrix} \] **(b) Solve the lower triangular system \( \mathbf{L}\mathbf{y} = \mathbf{b} \).** \[ y = \begin{bmatrix} \\ \\ \end{bmatrix} \rightarrow \] **(c) Solve the upper triangular system \( \mathbf{U}\mathbf{x} = \mathbf{y} \).** \[ x = \begin{bmatrix} \\ \\ \end{bmatrix} \rightarrow \] ### Diagram Explanation 1. **LU Decomposition:** - **Matrix \(\mathbf{L}\)**: A 3x3 lower triangular matrix with a unit diagonal (diagonal elements are 1). - **Matrix \(\mathbf{U}\)**: A 3x3 upper
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