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Use the given \(A\) and \(B\) to evaluate each expression. $$A=\left[\begin{array}{rrr}3 & -2 & 4 \\\5 & 2 & -3 \\\7 & 5 & 4\end{array}\right], B=\left[\begin{array}{rrr}1 & 1 & -5 \\\\-1 & 0 & -7 \\\\-6 & 4 & 3\end{array}\right]$$ $$B A$$

Short Answer

Expert verified
The product \( BA \) is \[ \left[ \begin{array}{ccc} -27 & -25 & -19 \\ -52 & -33 & -32 \\ 23 & 35 & -24 \end{array} \right] \] .

Step by step solution

01

Understand Matrix Multiplication

Matrix multiplication involves taking rows from the first matrix and columns from the second matrix. For two matrices, say matrix \( C \) of size \( m \times n \) and matrix \( D \) of size \( n \times p \), the resulting product is a matrix of size \( m \times p \). Here, matrix \( B \) is \( 3 \times 3 \) and matrix \( A \) is \( 3 \times 3 \), so the result \( BA \) will be a \( 3 \times 3 \) matrix.
02

Multiply First Row of B by A

Take the first row of \( B \), which is \([1, 1, -5]\), and multiply it with each column of \( A \).- For the first column: \( (1 \times 3) + (1 \times 5) + (-5 \times 7) = 3 + 5 - 35 = -27 \) - For the second column:\( (1 \times -2) + (1 \times 2) + (-5 \times 5) = -2 + 2 - 25 = -25 \)- For the third column:\( (1 \times 4) + (1 \times -3) + (-5 \times 4) = 4 - 3 - 20 = -19 \)Thus, the first row of \( BA \) is \([-27, -25, -19]\).
03

Multiply Second Row of B by A

Take the second row of \( B \), which is \([-1, 0, -7]\), and multiply it with each column of \( A \).- For the first column:\( (-1 \times 3) + (0 \times 5) + (-7 \times 7) = -3 + 0 - 49 = -52 \) - For the second column:\( (-1 \times -2) + (0 \times 2) + (-7 \times 5) = 2 + 0 - 35 = -33 \)- For the third column:\( (-1 \times 4) + (0 \times -3) + (-7 \times 4) = -4 + 0 - 28 = -32 \)Thus, the second row of \( BA \) is \([-52, -33, -32]\).
04

Multiply Third Row of B by A

Take the third row of \( B \), which is \([-6, 4, 3]\), and multiply it with each column of \( A \).- For the first column:\( (-6 \times 3) + (4 \times 5) + (3 \times 7) = -18 + 20 + 21 = 23 \) - For the second column:\( (-6 \times -2) + (4 \times 2) + (3 \times 5) = 12 + 8 + 15 = 35 \)- For the third column:\( (-6 \times 4) + (4 \times -3) + (3 \times 4) = -24 - 12 + 12 = -24 \)Thus, the third row of \( BA \) is \([23, 35, -24]\).
05

Construct the Resulting Matrix

Combine the rows obtained in steps 2, 3, and 4 to form matrix \( BA \): \[ BA = \left[ \begin{array}{ccc} -27 & -25 & -19 \ -52 & -33 & -32 \ 23 & 35 & -24 \end{array} \right] \]

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Key Concepts

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

Matrix Operations
Matrix operations are the foundational actions in matrix algebra, involving calculations and manipulations such as addition, subtraction, and multiplication. Among these, matrix multiplication is the most complex but essential operation.
Matrix multiplication requires following specific rules to produce a valid result. To multiply two matrices, the number of columns in the first matrix must be equal to the number of rows in the second matrix. This is crucial for ensuring that each element is paired appropriately.
Each element in the resulting matrix is calculated by taking the dot product of a row from the first matrix with a column from the second matrix. In our example, the matrices \(A\) and \(B\) have dimensions of \(3 \times 3\), allowing for multiplication to yield another \(3 \times 3\) matrix. Following the step-by-step calculation carefully helps ensure accuracy in compiling the resulting matrix.
Algebra
Algebra involves working with variables and constants to find unknowns or describe relationships using equations and mathematical expressions. It provides the framework necessary to manipulate and solve problems involving matrices.
In context with matrices, algebra comes into play when each element is treated as a variable part of a larger algebraic expression. Matrix multiplication, like in the equation \(BA=C\), is a great example of performing algebraic manipulation using defined rules and properties.
In this multiplication, each entry of matrix \(BA\) is derived from performing various algebraic operations such as multiplication and addition on entries from matrices \(B\) and \(A\). It's an application of linear equations where each element of the matrix can be thought of as a solution derived from these computations.
Linear Algebra
Linear algebra is a branch of mathematics that deals with vectors, matrices, and linear transformations. It plays a vital role in various scientific and engineering disciplines.
This field studies vector spaces and the linear mappings between these spaces, which often involve solving systems of linear equations. Matrices are fundamental here as they can represent both linear transformations and systems of equations.
Matrix operations such as multiplication, additions, and finding inverses are all linear algebra tasks. In the given exercise, multiplying matrices \(A\) and \(B\) showcases linear algebra's utility in real-world applications. Understanding these operations broadens the application of these mathematical solutions to complex problems in engineering, physics, and beyond.

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Most popular questions from this chapter

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