3 2 Let A = Write 2A. Is det(2A) equal to 2det(A)? 1 9 2A =

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Chapter2: Second-order Linear Odes
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**Matrix Scalar Multiplication and Determinant Properties**

**Problem Statement:**
Given a matrix \( A \) defined as:
\[ A = \begin{bmatrix} 3 & 2 \\ 1 & 9 \end{bmatrix} \]

1. Write \( 2A \).
2. Is \( \text{det}(2A) \) equal to \( 2 \cdot \text{det}(A) \)?

**Solution Steps:**

1. **Scalar Multiplication:**

   To find \( 2A \), multiply each element of matrix \( A \) by 2.

   \[ 2A = 2 \times \begin{bmatrix} 3 & 2 \\ 1 & 9 \end{bmatrix} = \begin{bmatrix} 2 \times 3 & 2 \times 2 \\ 2 \times 1 & 2 \times 9 \end{bmatrix} = \begin{bmatrix} 6 & 4 \\ 2 & 18 \end{bmatrix} \]

   Therefore, \( 2A \) is:
   \[ \begin{bmatrix} 6 & 4 \\ 2 & 18 \end{bmatrix} \]

2. **Determinant Calculation:**
   
   The determinant of a \( 2 \times 2 \) matrix \( M = \begin{bmatrix} a & b \\ c & d \end{bmatrix} \) is given by:
   \[ \text{det}(M) = ad - bc \]

   **First, calculate \( \text{det}(A) \):**

   For \( A = \begin{bmatrix} 3 & 2 \\ 1 & 9 \end{bmatrix} \),
   \[ \text{det}(A) = (3 \times 9) - (2 \times 1) = 27 - 2 = 25 \]

   **Next, calculate \( \text{det}(2A) \):**
   
   For \( 2A = \begin{bmatrix} 6 & 4 \\ 2 & 18 \end{bmatrix} \),
   \[ \text{det}(2A) = (6 \times 18) - (4 \times 2) = 108
Transcribed Image Text:**Matrix Scalar Multiplication and Determinant Properties** **Problem Statement:** Given a matrix \( A \) defined as: \[ A = \begin{bmatrix} 3 & 2 \\ 1 & 9 \end{bmatrix} \] 1. Write \( 2A \). 2. Is \( \text{det}(2A) \) equal to \( 2 \cdot \text{det}(A) \)? **Solution Steps:** 1. **Scalar Multiplication:** To find \( 2A \), multiply each element of matrix \( A \) by 2. \[ 2A = 2 \times \begin{bmatrix} 3 & 2 \\ 1 & 9 \end{bmatrix} = \begin{bmatrix} 2 \times 3 & 2 \times 2 \\ 2 \times 1 & 2 \times 9 \end{bmatrix} = \begin{bmatrix} 6 & 4 \\ 2 & 18 \end{bmatrix} \] Therefore, \( 2A \) is: \[ \begin{bmatrix} 6 & 4 \\ 2 & 18 \end{bmatrix} \] 2. **Determinant Calculation:** The determinant of a \( 2 \times 2 \) matrix \( M = \begin{bmatrix} a & b \\ c & d \end{bmatrix} \) is given by: \[ \text{det}(M) = ad - bc \] **First, calculate \( \text{det}(A) \):** For \( A = \begin{bmatrix} 3 & 2 \\ 1 & 9 \end{bmatrix} \), \[ \text{det}(A) = (3 \times 9) - (2 \times 1) = 27 - 2 = 25 \] **Next, calculate \( \text{det}(2A) \):** For \( 2A = \begin{bmatrix} 6 & 4 \\ 2 & 18 \end{bmatrix} \), \[ \text{det}(2A) = (6 \times 18) - (4 \times 2) = 108
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