Math Problem Statement

se the inverse matrices to find (AB)−1, (AT)−1, and (2A)−1. A−1 =

1 −2

−2 5 ,

B−1 =

1 2

−2 −3

Solution

Given the inverse matrices A1A^{-1} and B1B^{-1}, we can use matrix properties to find (AB)1(AB)^{-1}, (AT)1(A^T)^{-1}, and (2A)1(2A)^{-1}.

1. Finding (AB)1(AB)^{-1}:

By the property of the inverse of a product of matrices, we know: (AB)1=B1A1(AB)^{-1} = B^{-1}A^{-1} To find (AB)1(AB)^{-1}, we multiply the given matrices B1B^{-1} and A1A^{-1}.

Given: A1=(1225),B1=(1223)A^{-1} = \begin{pmatrix} 1 & -2 \\ -2 & 5 \end{pmatrix}, \quad B^{-1} = \begin{pmatrix} 1 & 2 \\ -2 & -3 \end{pmatrix}

Now, compute B1A1B^{-1}A^{-1}: B1A1=(1223)(1225)B^{-1}A^{-1} = \begin{pmatrix} 1 & 2 \\ -2 & -3 \end{pmatrix} \begin{pmatrix} 1 & -2 \\ -2 & 5 \end{pmatrix} Let's calculate this step by step.

2. Finding (AT)1(A^T)^{-1}:

By the property of transposed inverses: (AT)1=(A1)T(A^T)^{-1} = (A^{-1})^T So, we just take the transpose of A1A^{-1}.

Given A1=(1225)A^{-1} = \begin{pmatrix} 1 & -2 \\ -2 & 5 \end{pmatrix}, the transpose is: (A1)T=(1225)(A^{-1})^T = \begin{pmatrix} 1 & -2 \\ -2 & 5 \end{pmatrix} Thus, (AT)1=(1225)(A^T)^{-1} = \begin{pmatrix} 1 & -2 \\ -2 & 5 \end{pmatrix}.

3. Finding (2A)1(2A)^{-1}:

By the property of scalar multiples of matrices, we know: (2A)1=12A1(2A)^{-1} = \frac{1}{2} A^{-1} Thus, multiply A1A^{-1} by 12\frac{1}{2}: (2A)1=12(1225)=(121152)(2A)^{-1} = \frac{1}{2} \begin{pmatrix} 1 & -2 \\ -2 & 5 \end{pmatrix} = \begin{pmatrix} \frac{1}{2} & -1 \\ -1 & \frac{5}{2} \end{pmatrix}

Summary:

  1. (AB)1=B1A1(AB)^{-1} = B^{-1} A^{-1}
  2. (AT)1=(A1)T=(1225)(A^T)^{-1} = (A^{-1})^T = \begin{pmatrix} 1 & -2 \\ -2 & 5 \end{pmatrix}
  3. (2A)1=(121152)(2A)^{-1} = \begin{pmatrix} \frac{1}{2} & -1 \\ -1 & \frac{5}{2} \end{pmatrix}

Would you like to go through the detailed calculation of (AB)1(AB)^{-1}? Let me know if you have questions!

Here are some related questions you might consider:

  1. How do you compute the inverse of a matrix?
  2. What is the significance of the transpose in matrices?
  3. How does the determinant affect the inverse of a matrix?
  4. What is the property of the inverse of scalar multiples of matrices?
  5. How do inverse matrices apply to solving systems of equations?

Tip: When multiplying matrices, pay attention to the order—matrix multiplication is not commutative!

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Math Problem Analysis

Mathematical Concepts

Matrix Inverses
Matrix Transpose
Scalar Multiplication of Matrices

Formulas

(AB)^{-1} = B^{-1}A^{-1}
(A^T)^{-1} = (A^{-1})^T
(2A)^{-1} = \frac{1}{2}A^{-1}

Theorems

Inverse of a Product Theorem
Transpose of an Inverse Matrix Theorem
Inverse of a Scalar Multiple Theorem

Suitable Grade Level

College-Level Linear Algebra