/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 4 Compute matrix products column b... [FREE SOLUTION] | 91Ó°ÊÓ

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Compute matrix products column by column and entry by entry. Interpret matrix multiplication in terms of the underlying linear transformations. Use the rules of matrix algebra. Multiply block matrices. If possible, compute the matrix products using paper and pencil. $$\left[\begin{array}{rr} 1 & -1 \\ -2 & 2 \end{array}\right]\left[\begin{array}{ll} 7 & 5 \\ 3 & 1 \end{array}\right]$$

Short Answer

Expert verified
\[C = \begin{bmatrix} 4 & 4\ -8 & -8 \end{bmatrix}\]

Step by step solution

01

Understand Matrix Multiplication

The product of two matrices is found by multiplying the rows of the first matrix by the columns of the second matrix, and summing the products. For two matrices A (of size m x n) and B (of size n x p), the resulting matrix C will have the size m x p.
02

Determine the Size of the Resulting Matrix

Matrix A is a 2x2 matrix and matrix B is also a 2x2 matrix. Therefore, their product will also be a 2x2 matrix C.
03

Compute the First Column of the Product

For the first column of matrix C, multiply each element of the first column of matrix A by the corresponding element of the first row of matrix B, and then do the same for the second column of A with the second row of B; sum the results: C11 = (1)(7) + (-1)(3) = 4, C21 = (-2)(7) + (2)(3) = -8.
04

Compute the Second Column of the Product

Repeat the process for the second column of matrix C: C12 = (1)(5) + (-1)(1) = 4, C22 = (-2)(5) + (2)(1) = -8.
05

Write down the resulting matrix

The product of the given matrices is a 2x2 matrix C: \[C = \begin{bmatrix} 4 & 4\ -8 & -8 \end{bmatrix}\].

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Key Concepts

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

Matrix Algebra
Matrix algebra is a set of algebraic rules that govern the manipulation and operations of matrices. It's an essential part of linear algebra used to solve systems of linear equations and perform linear transformations in various fields like engineering, physics, computer science, and economics. Understanding how to multiply two matrices is a fundamental aspect of matrix algebra.

When multiplying two matrices, it's crucial to determine if the operation is valid. For matrices to be multiplied, the number of columns in the first matrix must equal the number of rows in the second. In our textbook exercise, both matrices are 2x2, so the multiplication is possible. Through a step-by-step analysis, like the provided exercise, individuals can find the resulting matrix by performing an element-wise multiplication followed by addition, as per the row-by-column rule. Remember that matrix multiplication is not commutative; switching the order of the factors can lead to different results or an undefined operation.
Linear Transformations
In mathematics, linear transformations are mappings between two vector spaces that preserve the operations of vector addition and scalar multiplication. Matrices are the standard tools for representing linear transformations, with each column of a matrix representing the transformation's effect on a particular basis vector.

Interpreting matrix multiplication in terms of linear transformations allows us to see the exercise's resultant matrix as a transformation that maps two-dimensional vectors into a new space according to specific rules. In essence, multiplying a vector by the resulting matrix will transform the vector in a linear manner, scaling, rotating, or shearing it based on the values in the original matrices. This visualization of matrix multiplication as linear transformations adds a geometrical perspective to the algebraic process and helps understand the deeper implications of matrix operations in fields like computer graphics and robotics.
Block Matrices
Block matrices are partitions of a matrix into submatrices, where each block behaves almost as an independent matrix. Manipulating block matrices can simplify matrix calculations, particularly with large matrices or systems with a naturally block-like structure. While not directly illustrated in our textbook problem, understanding block matrices can expand an individual's ability to work with and conceptualize large scale linear algebra problems.

In operations involving block matrices, we apply similar multiplication rules to each block as we would to a regular matrix multiplication. The crucial takeaway is that the rules of matrix algebra apply to these blocks, given the block dimensions are compatible. The concept greatly aids in simplifying complex matrix operations and is widely used in numerical analysis and parallel computations for breaking down large problems into more manageable subproblems.

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Most popular questions from this chapter

Show that if a square matrix \(A\) has two equal columns, then \(A\) is not invertible.

For the matrices \(A\) compute \(A^{2}=A A, A^{3}=A A A,\) and \(A^{4} .\) Describe the pattern that emerges, and use this pattern to find \(A^{1001}\). Interpret your answers geometrically, in terms of rotations, reflections, shears, and orthogonal projections. $$\left[\begin{array}{ll} 0 & 1 \\ 1 & 0 \end{array}\right]$$

In the financial pages of a newspaper, one can sometimes find a table (or matrix) listing the exchange rates between currencies. In this exercise we will consider a miniature version of such a table, involving only the Canadian dollar (C\$) and the South African Rand (ZAR). Consider the matrix \(\mathrm{CS} \quad \mathrm{ZAR}\) \\[ A=\left[\begin{array}{cc} 1 & 1 / 8 \\ 8 & 1 \end{array}\right] \begin{array}{c} \mathrm{CS} \\ \mathrm{ZAR} \end{array} \\] representing the fact that \(\mathrm{C} \$ 1\) is worth \(\mathrm{ZAR} 8\) (as of September 2012 ). a. After a trip you have \(\mathrm{C} \$ 100\) and \(\mathrm{ZAR} 1,600\) in your pocket. We represent these two values in the vector \(\vec{x}=\left[\begin{array}{c}100 \\ 1,600\end{array}\right] .\) Compute \(A \vec{x} .\) What is the practical significance of the two components of the vector \(A \vec{x} ?\) b. Verify that matrix \(A\) fails to be invertible. For which vectors \(\vec{b}\) is the system \(A \vec{x}=\vec{b}\) consistent? What is the practical significance of your answer? If the system \(A \vec{x}=\vec{b}\) is consistent, how many solutions \(\vec{x}\) are there? Again, what is the practical significance of the answer?

Find \(A^{-1}\) for \(A=\left[\begin{array}{rr}1 & k \\ 0 & -1\end{array}\right]\).

Find all matrices \(X\) that satisfy the given matrix equation. $$X\left[\begin{array}{ll} 2 & 1 \\ 4 & 2 \end{array}\right]=\left[\begin{array}{ll} 0 & 0 \\ 0 & 0 \end{array}\right]$$

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