Skip to main content
Ch. 5 - Systems and Matrices
Lial - College Algebra 13th Edition
Lial13th EditionCollege AlgebraISBN: 9780136881063Not the one you use?Change textbook
Chapter 6, Problem 2

Answer each question. What is the product [574230166][100010001]\(\left\)[ \(\begin{matrix}\) -5 & 7 & 4 \\2 & 3 & 0 \\-1 & 6 & 6 \(\end{matrix}\) \(\right\)]\(\quad\]\left\)[ \(\begin{matrix}\) 1 & 0 & 0 \\0 & 1 & 0 \\0 & 0 & 1 \(\end{matrix}\) \(\right\)]?

Verified step by step guidance
1
Identify the two 3x3 matrices given in the problem. Let's call the first matrix \( A \) and the second matrix \( B \).
Recall that the product of two matrices \( A \) and \( B \), where both are 3x3, is another 3x3 matrix \( C = AB \). Each element \( c_{ij} \) of matrix \( C \) is found by multiplying the elements of the \( i \)-th row of \( A \) by the corresponding elements of the \( j \)-th column of \( B \) and summing the results.
Write the formula for each element \( c_{ij} \) of the product matrix \( C \): \[ c_{ij} = a_{i1}b_{1j} + a_{i2}b_{2j} + a_{i3}b_{3j} \]
For each element in the resulting matrix \( C \), perform the multiplication and addition as per the formula above. Do this for all rows \( i = 1, 2, 3 \) and columns \( j = 1, 2, 3 \).
After calculating all nine elements \( c_{ij} \), arrange them into the 3x3 matrix \( C \), which is the product of the two given matrices.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
5m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Matrix Multiplication

Matrix multiplication involves multiplying rows of the first matrix by columns of the second matrix and summing the products. For two 3x3 matrices, each element in the product matrix is calculated by taking the dot product of a row from the first matrix and a column from the second matrix.
Recommended video:
03:42
Finding Zeros & Their Multiplicity

Dimensions and Compatibility

To multiply two matrices, the number of columns in the first matrix must equal the number of rows in the second. Since both matrices are 3x3, they are compatible for multiplication, and the resulting matrix will also be 3x3.

Properties of Matrix Multiplication

Matrix multiplication is associative and distributive but not commutative, meaning AB does not necessarily equal BA. Understanding these properties helps in correctly performing and interpreting matrix products.
Recommended video:
5:36
Change of Base Property