Table of contents
- 0. Review of Algebra4h 18m
- 1. Equations & Inequalities3h 18m
- 2. Graphs of Equations43m
- 3. Functions2h 17m
- 4. Polynomial Functions1h 44m
- 5. Rational Functions1h 23m
- 6. Exponential & Logarithmic Functions2h 28m
- 7. Systems of Equations & Matrices4h 6m
- 8. Conic Sections2h 23m
- 9. Sequences, Series, & Induction1h 22m
- 10. Combinatorics & Probability1h 45m
7. Systems of Equations & Matrices
Determinants and Cramer's Rule
Problem 7
Textbook Question
In Exercises 1 - 12, find the products AB and BA to determine whether B is the multiplicative inverse of A. 0 1 0 0 0 1A = 0 0 1 B = 1 0 01 0 0 0 1 0

1
Multiply matrix A by matrix B to find the product AB.
For AB, calculate the first row, first column element: (0*0 + 1*1 + 0*0).
For AB, calculate the first row, second column element: (0*0 + 1*0 + 0*1).
For AB, calculate the first row, third column element: (0*1 + 1*0 + 0*0).
Repeat the process for the remaining elements of AB and then calculate BA similarly.

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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Matrix Multiplication
Matrix multiplication involves taking the rows of the first matrix and the columns of the second matrix to produce a new matrix. The element in the resulting matrix is calculated by summing the products of corresponding entries. This operation is not commutative, meaning that AB does not necessarily equal BA.
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Identity Matrix
An identity matrix is a square matrix with ones on the diagonal and zeros elsewhere. It acts as the multiplicative identity in matrix multiplication, meaning that for any matrix A, multiplying by the identity matrix I results in A (AI = A and IA = A). The identity matrix is crucial for determining if a matrix has an inverse.
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Multiplicative Inverse
A matrix B is considered the multiplicative inverse of matrix A if the products AB and BA both equal the identity matrix. This means that multiplying A by B (and vice versa) effectively 'cancels out' A, demonstrating that B undoes the transformation represented by A. Finding the inverse is essential in solving systems of equations and other applications.
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