Math Problem Statement

Let A and B be square matrices of order 4 such that |A| = –6 and |B| = –6. Find the following.

(a)    |AB|

(b)    |A3|

(c)    |3B|

(d)    |(AB)T|

(e)    |A−1|

Solution

Given that AA and BB are square matrices of order 4 with determinants A=6|A| = -6 and B=6|B| = -6, we can use the properties of determinants to find the required values.

(a) AB|AB|

The determinant of the product of two matrices is the product of their determinants:

AB=AB=(6)(6)=36|AB| = |A| \cdot |B| = (-6) \cdot (-6) = 36

(b) A3|A^3|

The determinant of a matrix raised to a power nn is the determinant of the matrix raised to that power:

A3=A3=(6)3=216|A^3| = |A|^3 = (-6)^3 = -216

(c) 3B|3B|

If cc is a scalar and BB is a matrix of order nn, then the determinant of the scalar multiple is given by:

cB=cnB|cB| = c^n \cdot |B|

Since BB is a 4x4 matrix, n=4n = 4, and c=3c = 3:

3B=34B=81(6)=486|3B| = 3^4 \cdot |B| = 81 \cdot (-6) = -486

(d) (AB)T|(AB)^T|

The determinant of a matrix is equal to the determinant of its transpose:

(AB)T=AB=36|(AB)^T| = |AB| = 36

(e) A1|A^{-1}|

The determinant of the inverse of a matrix is the reciprocal of the determinant:

A1=1A=16=16|A^{-1}| = \frac{1}{|A|} = \frac{1}{-6} = -\frac{1}{6}

Summary of Results:

(a) AB=36\text{(a)}\ |AB| = 36 (b) A3=216\text{(b)}\ |A^3| = -216 (c) 3B=486\text{(c)}\ |3B| = -486 (d) (AB)T=36\text{(d)}\ |(AB)^T| = 36 (e) A1=16\text{(e)}\ |A^{-1}| = -\frac{1}{6}

Would you like further explanation on any of these points, or do you have any other questions?

Here are 8 follow-up questions related to this topic:

  1. How does the determinant of a matrix change if the matrix is multiplied by a scalar?
  2. What does the determinant tell us about the invertibility of a matrix?
  3. How would you find the determinant of a product of three matrices?
  4. What happens to the determinant if a matrix is transposed?
  5. What is the determinant of the identity matrix of any order?
  6. How do you compute the determinant of a block matrix?
  7. Can a matrix with a determinant of zero be inverted? Why or why not?
  8. What are the implications of a negative determinant for a matrix?

Tip: Remember that the determinant provides important insights into the matrix, such as its invertibility and how it scales volume in linear transformations.

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Math Problem Analysis

Mathematical Concepts

Determinants
Matrix Algebra

Formulas

Determinant of a product of matrices
Determinant of a matrix raised to a power
Determinant of a scalar multiple
Determinant of the transpose of a matrix
Determinant of the inverse of a matrix

Theorems

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Suitable Grade Level

Advanced High School