/*! 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 60 Let \(A\) and \(B\) be two matri... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

Let \(A\) and \(B\) be two matrices such that the product \(A B\) is defined. Show that if \(A\) has two identical rows, then the corresponding two rows of \(A B\) are also identical.

Short Answer

Expert verified
If a matrix \(A\) has two identical rows, then the corresponding two rows of the product \(A B\) are also identical. This is due to the rules of matrix multiplication, which imply that corresponding elements of the product matrix are calculated in the same way from the identical rows of the first (leftmost) matrix.

Step by step solution

01

Defining the situation

Let's assume that matrix \(A\) has two identical rows. To be specific, let's say that the \(i^{th}\) and \(j^{th}\) rows of matrix \(A\) are identical (i.e., for every column \(k\), \(A[i,k] = A[j,k]\)).
02

Matrix multiplication rules

According to the rules of matrix multiplication, each element of the product matrix \(AB\) at position \([i,m]\) is calculated as the sum of the product of elements from the \(i^{th}\) row of matrix \(A\) and the \(m^{th}\) column of matrix \(B\). Formally, this is represented as \((AB)[i,m] = \sum_{n} A[i,n] * B[n,m]\).
03

Apply the given condition

As per the given condition, the \(i^{th}\) and \(j^{th}\) rows of matrix \(A\) are identical. So, this means that for every column \(n\) of matrix \(A\), \(A[i,n] = A[j,n]\). We can replace \(A[i,n]\) with \(A[j,n]\) in the matrix multiplication formula we established in the previous step.
04

Derived the identical rows in product matrix

Doing this, the sum from the previous step becomes: \((AB)[i,m] = \sum_{n} A[j,n] * B[n,m]\). And this is exactly the formula we would use if we were calculating the element at position [j, m] in the product matrix. Therefore, this means that \((AB)[i,m] = (AB)[j,m]\), meaning that the \(i^{th}\) and \(j^{th}\) rows in the product matrix are identical.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

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

Identical Rows in Matrices
In the realm of linear algebra, dealing with matrices often involves understanding their properties and how they interact. One interesting aspect is what happens when two rows in a matrix are identical. If a matrix \(A\) has two identical rows, say the \(i^{th}\) and \(j^{th}\) rows, this characteristic follows through to its matrix product with another matrix \(B\).

Consider this: when you multiply matrix \(A\) by matrix \(B\), each row of the resulting matrix is formed by the dot product of the rows of \(A\) with the columns of \(B\). Given the identical rows \(i\) and \(j\) in \(A\), any multiplication with columns from matrix \(B\) will produce identical results. Therefore, the product matrix \(AB\) will also have identical \(i^{th}\) and \(j^{th}\) rows.

This concept is fundamental because it shows that some properties of matrices are preserved through operations like multiplication. It highlights the inherent symmetry and repeating patterns in linear algebra, which can simplify computations.
Matrix Product Properties
Matrix multiplication is key in various applications of linear algebra and has unique properties that set it apart from other operations. Understanding these properties helps in comprehending larger mathematical and computational problems. Here are some important ones:
  • **Non-Commutative Nature:** In general, \(A \times B eq B \times A\). So, the order of multiplication matters greatly.
  • **Associative Law:** \((A \times B) \times C = A \times (B \times C)\). This property allows for the grouping of operations to simplify calculations.
  • **Distributive Over Addition:** \(A \times (B + C) = A \times B + A \times C\). This is useful for breaking down complex problems into simpler parts.

The property of preserving identical rows is part of the rich suite of matrix behaviors and ensures reliability in predicting the results of operations. This trustworthy pattern helps significantly in simplifying proofs and solving equations that involve matrices.
Linear Algebra Concepts
Linear algebra is a branch of mathematics that is fundamental to many scientific fields. It studies vectors, matrices, and linear transformations. Concepts like matrix multiplication are at its core and are pivotal in understanding system behaviors in coordinated spaces.

Here's a quick rundown of some fundamental concepts:
  • **Matrices and Vectors:** At the heart of linear algebra, matrices like \(A\) and \(B\) allow for representation of linear equations and transformations. Vectors are treated as matrices with a single column or row.
  • **Linear Transformations:** By applying matrix operations, we can transform a vector to be expressed in terms of another space. These transformations are essential in fields like computer graphics and quantum physics.
  • **Eigenvalues and Eigenvectors:** These are key in many applications, understood by how linear transformations stretch or compress a vector.

With these concepts, we build a framework that is not only theoretically intriguing but also practically imperative across various technical domains. Recognizing patterns such as identical row preservation leverages the structured nature of matrices to solve complex problems effectively.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

Factor the matrix \(A\) into a product of elementary matrices. $$A=\left[\begin{array}{lll} 1 & 2 & 3 \\ 2 & 5 & 6 \\ 1 & 3 & 4 \end{array}\right]$$

Express the column matrix b as a linear combination of the columns of \(A\) $$A=\left[\begin{array}{rr} -3 & 5 \\ 3 & 4 \\ 4 & -8 \end{array}\right], \quad \mathbf{b}=\left[\begin{array}{r} -22 \\ 4 \\ 32 \end{array}\right]$$

A population of 10,000 is grouped as follows: 5000 nonsmokers, 2500 smokers of one pack or less per day, and 2500 smokers of more than one pack per day. During any month there is a \(5 \%\) probability that a nonsmoker will begin smoking a pack or less per day, and a \(2 \%\) probability that a nonsmoker will begin smoking more than a pack per day. For smokers who smoke a pack or less per day, there is a \(10 \%\) probability of quitting and a \(10 \%\) probability of increasing to more than a pack per day. For smokers who smoke more than a pack per day, there is a \(5 \%\) probability of quitting and a \(10 \%\) probability of dropping to a pack or less per day. How many people will be in each of the 3 groups in 1 month? In 2 months?

The columns of matrix \(T\) show the coordinates of the vertices of a triangle. Matrix \(A\) is a transformation matrix. $$A=\left[\begin{array}{rr} 0 & -1 \\ 1 & 0 \end{array}\right], \quad T=\left[\begin{array}{lll} 1 & 2 & 3 \\ 1 & 4 & 2 \end{array}\right]$$ (a) Find \(A T\) and \(A A T .\) Then sketch the original triangle and the two transformed triangles. What transformation does \(A\) represent? (b) A triangle is determined by \(A A T .\) Describe the transformation process that produces the triangle determined by \(A T\) and then the triangle determined by \(T\)

A fruit grower raises two crops, apples and peaches. Each of these crops is shipped to three different outlets. The number of units of crop \(i\) that are shipped to outlet \(j\) is represented by \(a_{i j}\) in the matrix $$A=\left[\begin{array}{lll} 125 & 100 & 75 \\ 100 & 175 & 125 \end{array}\right]$$ The profit per unit is represented by the matrix \\[ B=\left[\begin{array}{ll} \$ 3.50 & \$ 6.00 \end{array}\right] \\] Find the product \(B A\) and state what each entry of the product represents.

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.