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Evaluate the determinant of the matrix. $$\left[\begin{array}{rrr} -5 & 4 & 9 \\ 1 & 0 & -2 \\ 0 & 7 & 3 \end{array}\right]$$

Short Answer

Expert verified
The determinant of the given matrix is -19.

Step by step solution

01

Setup the Formula

For any 3x3 matrix \(A = a_{ij}\), the determinant is calculated by the formula: \(\det(A) = a_{11}(a_{22}a_{33} - a_{23}a_{32}) - a_{12}(a_{21}a_{33} - a_{23}a_{31}) + a_{13}(a_{21}a_{32} - a_{22}a_{31})\). In our case, the matrix is \(A = \left[\begin{array}{rrr} -5 & 4 & 9 \ 1 & 0 & -2 \ 0 & 7 & 3 \end{array}\right]\). Hence, \(a_{11} = -5\), \(a_{12} = 4\), \(a_{13} = 9\), \(a_{21} = 1\), \(a_{22} = 0\), \(a_{23} = -2\), \(a_{31} = 0\), \(a_{32} = 7\) and \(a_{33} = 3\).
02

Substitute into the Formula

Substitute all \(a_{ij}\) values from the matrix into the determinant formula. Hence, \(\det(A) = -5(0*3 - -2*7) - 4(1*3 - -2*0) + 9(1*7 - 0*0)\).
03

Evaluate the Determinant

Evaluate each mini expression inside the big brackets separately. Hence, \(\det(A) = -5(14) - 4(3) + 9(7)\). Now, calculate it to obtain the determinant value. \(\det(A) = -70 - 12 + 63 = -19.\)

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Understanding Matrix Algebra
Matrix Algebra is a branch of mathematics that deals with matrices. A matrix is a rectangular array of numbers arranged in rows and columns. Understanding how to perform operations with matrices is fundamental as they serve various purposes in mathematics and applied sciences.

There are different operations you can perform on matrices, such as addition, subtraction, and multiplication. However, in this discussion, we will focus on an essential operation called the determinant. In matrix algebra, determinants provide insights into various properties of a matrix, such as invertibility and volume scaling when considering linear transformations.
  • Determinant provides a scalar value that reflects certain characteristics of a matrix.
  • Helps determine if a matrix is invertible. If the determinant is zero, the matrix is not invertible.
  • Used importantly in solving systems of linear equations.
  • Calculations involving determinants are common in matrix algebra.
Mastering matrix algebra, including determinants, allows you to understand more complex mathematical and real-world concepts.
Exploring a 3x3 Matrix
A 3x3 matrix is a specific type of matrix composed of three rows and three columns. It's a common matrix size in many algebra problems because it is manageable yet complex enough to illustrate important concepts, such as computing determinants.

The general representation of a 3x3 matrix looks like this:\[\begin{bmatrix}a_{11} & a_{12} & a_{13} \a_{21} & a_{22} & a_{23} \a_{31} & a_{32} & a_{33} \end{bmatrix}\]Each element in the matrix is identified by two subscripts representing the row and column of the matrix.
  • 3x3 matrix elements represented as \(a_{ij}\) indicate their position.
  • Used frequently when performing transformations and operations in linear algebra.
  • Essential for evaluating determinants using concise formulas.
Exploring a 3x3 matrix helps in understanding how to handle more intricate matrices and build foundation knowledge for further studies.
Evaluating Determinants in a 3x3 Matrix
Evaluating the determinant of a 3x3 matrix involves a specific formula that calculates a single number, which offers valuable information about the matrix.

The formula for the determinant of a 3x3 matrix \(A\) is:\[det(A) = a_{11}(a_{22}a_{33} - a_{23}a_{32}) - a_{12}(a_{21}a_{33} - a_{23}a_{31}) + a_{13}(a_{21}a_{32} - a_{22}a_{31})\]This formula is derived from breaking down the main matrix components, focusing on finding the minor determinants, and applying cofactor expansion.
  • Separate calculations into smaller expressions, solving piece by piece.
  • Pay attention to signs (positive or negative) associated with each term in the expansion formula.
  • Resulting value indicates several matrix properties, helpful in solving varied mathematical problems.
Mastering the evaluation of determinants simplifies the handling of more complex matrix operations, beneficial for deeper computational tasks.

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