Compute the following determinant by cofactor expansions. At each step, choose the row or column that involves the least amount of 1-2 42 0 0 20 5 -4 -5 3 30 35 The determinant is ...

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
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Chapter2: Second-order Linear Odes
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### Determinant Calculation Using Cofactor Expansions

**Exercise:**
Compute the following determinant by cofactor expansions. At each step, choose the row or column that involves the least amount of computation.

\[
\begin{vmatrix}
1 & -2 & 4 & 2 \\
0 & 0 & 2 & 0 \\
5 & -4 & -5 & 3 \\
3 & 0 & 3 & 5 
\end{vmatrix}
\]

---

### Explanation:

1. **Matrix Provided:**
   \[
   \begin{bmatrix}
   1 & -2 & 4 & 2 \\
   0 & 0 & 2 & 0 \\
   5 & -4 & -5 & 3 \\
   3 & 0 & 3 & 5 
   \end{bmatrix}
   \]

2. **Steps:**
   - Identify the row or column with the most zeros to minimize computation.
   - Apply cofactor expansion on the selected row or column.

**Note:** Here, the second row has the most zeros \( [0, 0, 2, 0] \), which simplifies the computation significantly.

3. **Expansion Process:**  
   Expanding along the second row:
   - The second row is \( [0, 0, 2, 0] \)
   - Only the third element (2) is non-zero.
   - The corresponding minor matrix for this element is obtained by deleting the row and column containing this element.
   
   \[
   \begin{vmatrix}
   1 & -2 & 2 \\
   5 & -4 & 3 \\
   3 & 0 & 5 
   \end{vmatrix}
   \]

4. **Continue with 3x3 Determinant:**  
   Compute the determinant of the above 3x3 matrix using cofactor expansion on the row or column with the least non-zero elements for simplification.

---

### Conclusion:

After following the necessary steps of cofactor expansion, the determinant can be computed.

**Answer:**
The determinant is [ ____ ].

---

### Graphs or Diagrams:
- There are no additional graphs or diagrams in the provided content.
Transcribed Image Text:### Determinant Calculation Using Cofactor Expansions **Exercise:** Compute the following determinant by cofactor expansions. At each step, choose the row or column that involves the least amount of computation. \[ \begin{vmatrix} 1 & -2 & 4 & 2 \\ 0 & 0 & 2 & 0 \\ 5 & -4 & -5 & 3 \\ 3 & 0 & 3 & 5 \end{vmatrix} \] --- ### Explanation: 1. **Matrix Provided:** \[ \begin{bmatrix} 1 & -2 & 4 & 2 \\ 0 & 0 & 2 & 0 \\ 5 & -4 & -5 & 3 \\ 3 & 0 & 3 & 5 \end{bmatrix} \] 2. **Steps:** - Identify the row or column with the most zeros to minimize computation. - Apply cofactor expansion on the selected row or column. **Note:** Here, the second row has the most zeros \( [0, 0, 2, 0] \), which simplifies the computation significantly. 3. **Expansion Process:** Expanding along the second row: - The second row is \( [0, 0, 2, 0] \) - Only the third element (2) is non-zero. - The corresponding minor matrix for this element is obtained by deleting the row and column containing this element. \[ \begin{vmatrix} 1 & -2 & 2 \\ 5 & -4 & 3 \\ 3 & 0 & 5 \end{vmatrix} \] 4. **Continue with 3x3 Determinant:** Compute the determinant of the above 3x3 matrix using cofactor expansion on the row or column with the least non-zero elements for simplification. --- ### Conclusion: After following the necessary steps of cofactor expansion, the determinant can be computed. **Answer:** The determinant is [ ____ ]. --- ### Graphs or Diagrams: - There are no additional graphs or diagrams in the provided content.
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