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Check the statements in Exercises \(19-23\) using the matrices \(\mathbf{U}=\left(\begin{array}{ll}2 & 3 \\ 1 & 2\end{array}\right), \mathbf{V}=\left(\begin{array}{cc}-1 & 4 \\ 0 & 2\end{array}\right), \mathbf{W}=\left(\begin{array}{cc}5 & -5 \\ 4 & 7\end{array}\right)\) $$ \mathbf{U}+\mathbf{W}=\mathbf{W}+\mathbf{U} $$

Short Answer

Expert verified
Answer: True

Step by step solution

01

Find \(\mathbf{U}+\mathbf{W}\)

To find the sum of two matrices, add the corresponding elements of the matrices. In this case: $\mathbf{U}+\mathbf{W}= \left(\begin{array}{cc} 2 & 3 \\ 1 & 2 \end{array}\right) + \left(\begin{array}{cc} 5 & -5 \\ 4 & 7 \end{array}\right) = \left(\begin{array}{cc} 2+5 & 3+(-5) \\ 1+4 & 2+7 \end{array}\right) = \left(\begin{array}{cc} 7 & -2 \\ 5 & 9 \end{array}\right)$
02

Find \(\mathbf{W}+\mathbf{U}\)

Similarly, we find the sum of matrices W and U: $\mathbf{W}+\mathbf{U}= \left(\begin{array}{cc} 5 & -5 \\ 4 & 7 \end{array}\right) + \left(\begin{array}{cc} 2 & 3 \\ 1 & 2 \end{array}\right) = \left(\begin{array}{cc} 5+2 & (-5)+3 \\ 4+1 & 7+2 \end{array}\right) = \left(\begin{array}{cc} 7 & -2 \\ 5 & 9 \end{array}\right)$
03

Compare the results

Now, we can compare the results of the two additions: $\mathbf{U}+\mathbf{W} = \left(\begin{array}{cc} 7 & -2 \\ 5 & 9 \end{array}\right) \quad \text{and} \quad \mathbf{W}+\mathbf{U}= \left(\begin{array}{cc} 7 & -2 \\ 5 & 9 \end{array}\right)$ Since \(\mathbf{U}+\mathbf{W}\) is equal to \(\mathbf{W}+\mathbf{U}\), the given statement is true.

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Key Concepts

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

Associative Property
Associative property is all about grouping. In mathematics, this property tells us that no matter how we group the numbers (or matrices, in this case) when we're adding or multiplying, the result will be the same.

For matrices, the associative property for addition can be expressed as:
  • \((\mathbf{A} + \mathbf{B}) + \mathbf{C} = \mathbf{A} + (\mathbf{B} + \mathbf{C})\)
This means it doesn't matter if you add the first two matrices first or the last two; you'll end up with the same final result. Associative property ensures the order we add them in doesn't affect the outcome.

Understanding this is crucial because it allows flexibility in calculation methods. Whether simplifying complex equations or programming algorithms, associative property eases the process.
Commutative Property
When we talk about the commutative property, think of switching places. This property states that the order doesn't matter when adding or multiplying numbers or matrices.

For matrices in addition, the commutative property can be written as:
  • \(\mathbf{A} + \mathbf{B} = \mathbf{B} + \mathbf{A}\)
In the exercise, we see this with \(\mathbf{U} + \mathbf{W} = \mathbf{W} + \mathbf{U}\). By computing each side, you verify that switching the order of matrices doesn't change the sum. This property is fundamental, especially in simplifying algebraic expressions involving matrices.

Remember, while this works for addition, it's not the same for matrix multiplication. There, order can affect the result! But in addition, feel free to swap them around.
Matrices
Matrices are powerful mathematical tools used to organize and manipulate information. They are essentially rectangular arrays of numbers, which can be used to represent systems of equations, transformations, and more.

Key aspects of matrices include:
  • The size or dimension, usually given as \(m \times n\), where \(m\) tells you the number of rows and \(n\) the number of columns.
  • Elements inside a matrix are arranged in rows and columns and are usually denoted by their position, like \(a_{ij}\) for element in row \(i\) and column \(j\).
Matrix operations, including addition and multiplication, follow specific rules.

When adding two matrices, they must have the same dimensions. Simply add corresponding elements from each matrix to get the result. This is why you add element by element in matrix addition – each element from the first matrix combines with the one in the same position in the second. Thus, matrix addition is a straightforward extension of basic arithmetic to organized data.

Becoming familiar with matrices is crucial for fields like engineering, physics, and computer science, where complex data is commonplace.

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Most popular questions from this chapter

A manufacturer produces three different types of widgets and ships them to two different warehouses. The number of widgets shipped, \(\mathbf{W},\) and the price of the widgets, \(\mathbf{P},\) are given by $$ \mathbf{W}=\left(\begin{array}{cc} 900 & 3500 \\ 2250 & 1200 \\ 3310 & 1500 \end{array}\right), \quad \mathbf{P}=\left(\begin{array}{lll} 25 & 15 & 10 \end{array}\right) $$ The columns of \(\mathbf{W}\) correspond to the two warehouses and the rows to the three types of widgets. The columns of \(\mathbf{P}\) are the prices of the three types of widgets. (a) Calculate \(\mathbf{P W}\). (b) Explain the practical meaning of \(\mathbf{P W}\). (c) How much more widget inventory (in dollars) does the second warehouse contain?

Write the system of equations (a) In the form \(\mathbf{M} \vec{v}=\vec{w}\). (b) As an augmented matrix. $$ \left\\{\begin{aligned} 2 x+3 y+6 z &=6 z+15 \\ 3 z &=x-y+19 \\ -3 y+17 &=4 x-7 \end{aligned}\right. $$

Check the statements in Exercises \(19-23\) using the matrices \(\mathbf{U}=\left(\begin{array}{ll}2 & 3 \\ 1 & 2\end{array}\right), \mathbf{V}=\left(\begin{array}{cc}-1 & 4 \\ 0 & 2\end{array}\right), \mathbf{W}=\left(\begin{array}{cc}5 & -5 \\ 4 & 7\end{array}\right)\). $$ 2 \mathbf{W}+3 \mathbf{W}=5 \mathbf{W} $$

Find a single vector resulting from the operations. \(\left(\begin{array}{lll}0.6 & 0.2 & 0 \\ 0.4 & 0.8 & 1\end{array}\right)\left(\begin{array}{c}70 \\ 120 \\ 50\end{array}\right)\)

If possible, use row operations to solve the systems. $$ \left\\{\begin{array}{l} 5 x+3 y=4 \\ x+7 y=20 \end{array}\right. $$

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