Math Problem Statement

explain why det F became 0

Find the value of scalar a if a = det(F) - det(D). Explain why det(F) = 0.

Solution

To solve the problem and find the value of the scalar aa given as a=det(F)det(D)a = \text{det}(F) - \text{det}(D), and to explain why det(F)=0\text{det}(F) = 0, we need to calculate the determinants of matrices FF and DD.

Calculation of det(D)\text{det}(D)

Matrix DD is a diagonal matrix, which simplifies the determinant calculation. The determinant of a diagonal matrix is simply the product of the diagonal elements. Therefore, det(D)=14916=576.\text{det}(D) = 1 \cdot 4 \cdot 9 \cdot 16 = 576.

Calculation of det(F)\text{det}(F)

Matrix FF is more complex. To find the determinant, we can perform row operations to simplify the matrix without changing the determinant, or calculate directly if simplification is tricky. Looking at matrix FF, we can check for any row operations that simplify the calculation:

1 & -2 & 4 & -3 & 1 \\ 0 & -1 & 2 & 4 & 2 \\ 1 & 6 & -12 & 9 & -3 \\ -3 & 6 & -12 & 9 & -3 \\ 0 & 0 & 12 & 1 & 1 \end{bmatrix}$$ We can immediately notice that the third row and the fourth row are proportional: $$\text{Row 4} = -3 \times (\text{Row 3}) + \text{Row 1}.$$ This relationship indicates that the rows are linearly dependent. A matrix with linearly dependent rows has a determinant of zero. Thus, $$\text{det}(F) = 0$$. ### Conclusion Given $$\text{det}(F) = 0$$ and $$\text{det}(D) = 576$$, the value of scalar $$a$$ is: $$a = \text{det}(F) - \text{det}(D) = 0 - 576 = -576.$$ If you have any questions or need further details, feel free to ask. Here are some related questions you might consider: 1. How would you calculate the determinant of a 5x5 matrix without any obvious simplifications? 2. What properties of determinants can be useful in simplifying the calculation of a determinant? 3. Can you identify situations where the determinant of a matrix might be zero without doing calculations? 4. How would the result change if the matrices $$F$$ and $$D$$ were modified slightly? 5. What is the geometric interpretation of the determinant being zero? **Tip:** When you encounter a complex determinant calculation, consider using row and column operations to simplify the matrix while preserving the determinant’s value. This often includes making zeros to form an upper or lower triangular matrix, making the determinant calculation straightforward as the product of diagonal entries.

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Math Problem Analysis

Mathematical Concepts

Matrix Determinants
Linear Algebra

Formulas

det(F) = det(Matrix F)
det(D) = det(Matrix D)
Determinant of a diagonal matrix = product of diagonal elements

Theorems

Determinant of a diagonal matrix
Property of determinants: det of matrix with linearly dependent rows = 0

Suitable Grade Level

Undergraduate Linear Algebra