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Ch. 5 - Systems and Matrices
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063당신이 사용하는 게 아니라요?교과서 변경
6장, 문제 84

Find AB and BA for the following matrices.
A=[abcd]andB=[1001]A = \(\left\)[ \(\begin{matrix}\) a & b \\ c & d \(\end{matrix}\) \(\right\)] \(\quad\) \(\text{and}\) \(\quad\) B = \(\left\)[ \(\begin{matrix}\) 1 & 0 \\ 0 & 1 \(\end{matrix}\) \(\right\)]
Matrix B acts as the multiplicative element for 2 ×\(\times\) 2 square matrices.

검증된 단계별 안내
1
First, identify the matrices A and B explicitly. Since the problem statement does not provide the actual entries of matrices A and B, you need to write down or obtain the elements of both matrices. Each should be a 2x2 matrix, for example, \( A = \begin{bmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{bmatrix} \) and \( B = \begin{bmatrix} b_{11} & b_{12} \\ b_{21} & b_{22} \end{bmatrix} \).
To find the product \( AB \), multiply matrix A by matrix B using the rule for matrix multiplication: the element in the \( i^{th} \) row and \( j^{th} \) column of \( AB \) is calculated as \( (AB)_{ij} = a_{i1}b_{1j} + a_{i2}b_{2j} \). Perform this for all four elements to get the resulting 2x2 matrix.
Similarly, to find the product \( BA \), multiply matrix B by matrix A using the same matrix multiplication rule: \( (BA)_{ij} = b_{i1}a_{1j} + b_{i2}a_{2j} \). Calculate each element to form the resulting 2x2 matrix.
Remember that matrix multiplication is generally not commutative, so \( AB \) and \( BA \) may not be the same matrix. Carefully compute each product separately.
After computing both products, write down the resulting matrices \( AB \) and \( BA \) explicitly, showing all intermediate multiplication and addition steps for clarity.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Matrix Multiplication

Matrix multiplication involves combining two matrices by taking the dot product of rows from the first matrix with columns from the second. For two 2x2 matrices, each element of the product is calculated by multiplying corresponding elements and summing them. The order of multiplication matters, so AB and BA can yield different results.
추천 영상:
03:42
Finding Zeros & Their Multiplicity

Properties of 2x2 Matrices

A 2x2 matrix has four elements arranged in two rows and two columns. Operations like addition, multiplication, and finding inverses are defined specifically for this size. Understanding the structure helps in performing calculations accurately and recognizing special properties like the identity matrix.
추천 영상:
4:35
Introduction to Matrices

Multiplicative Identity Matrix

The multiplicative identity for 2x2 matrices is the identity matrix, which has ones on the diagonal and zeros elsewhere. Multiplying any 2x2 matrix by the identity matrix leaves it unchanged. Recognizing this matrix helps in understanding the role of matrix B as a multiplicative element.
추천 영상:
03:42
Finding Zeros & Their Multiplicity