Evaluate each determinant. ∣120−12−1014∣\left| \begin{matrix} 1 & 2 & 0 \\ -1 & 2 & -1 \\ 0 & 1 & 4 \end{matrix} \right|

Ch. 5 - Systems and Matrices

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Lial 13th Edition

Ch. 5 - Systems and Matrices

문제 23

6장, 문제 23

Evaluate each determinant.
$∣ \begin{matrix} 1 & 2 & 0 \\ - 1 & 2 & - 1 \\ 0 & 1 & 4 \end{matrix} ∣$

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Identify the size of the matrix for which you need to evaluate the determinant (e.g., 2x2, 3x3, etc.). The method depends on the matrix size.

For a 2x2 matrix $\begin{bmatrix} a & b \\ c & d \end{bmatrix}$, use the formula for the determinant: $\det = ad - bc$.

For a 3x3 matrix $\begin{bmatrix} a & b & c \\ d & e & f \\ g & h & i \end{bmatrix}$, apply the rule of Sarrus or cofactor expansion to find the determinant.

If using cofactor expansion for a 3x3 matrix, select a row or column, then calculate the sum of each element multiplied by its cofactor: $\det = a \cdot C_{11} + b \cdot C_{12} + c \cdot C_{13}$, where each cofactor $C_{ij} = (-1)^{i+j}$ times the determinant of the minor matrix obtained by removing row $i$ and column $j$.

Calculate each minor determinant and apply the signs accordingly, then sum all the terms to find the determinant of the matrix.

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Determinant of a Matrix

The determinant is a scalar value computed from a square matrix that provides important properties about the matrix, such as invertibility. For a 2x2 matrix, it is calculated as ad - bc, where a, b, c, and d are the elements of the matrix. Determinants help in solving systems of linear equations and understanding matrix behavior.

Methods for Calculating Determinants

Determinants can be calculated using various methods depending on the matrix size, including expansion by minors, cofactor expansion, and row reduction. For larger matrices, breaking down into smaller matrices or using properties like linearity simplifies the process. Understanding these methods is essential for efficient evaluation.

Properties of Determinants

Determinants have key properties such as changing sign when two rows are swapped, being zero if rows are linearly dependent, and the determinant of a product equals the product of determinants. These properties aid in simplifying calculations and interpreting the results in algebraic contexts.

Evaluate each determinant. ∣120−12−1014∣\(\left\)| \(\begin{matrix}\) 1 & 2 & 0 \\ -1 & 2 & -1 \\ 0 & 1 & 4 \(\end{matrix}\) \(\right\)|