Math Problem Statement

Find the determinant of AB^-1, given 2A - B = [[-5, 3], [4, 7]] and A - 2B = [[-5, 4], [3, 2]]

Solution

Let's break down the given problem and solve it step by step.

You are provided with two matrix equations:

  1. 2AB=[5347]2A - B = \begin{bmatrix} -5 & 3 \\ 4 & 7 \end{bmatrix}
  2. A2B=[5432]A - 2B = \begin{bmatrix} -5 & 4 \\ 3 & 2 \end{bmatrix}

You are asked to find the determinant of det(AB1)\text{det}(AB^{-1}).

Step-by-step approach:

  1. Solve for matrices AA and BB:

    • From the first equation: 2AB=[5347]2A - B = \begin{bmatrix} -5 & 3 \\ 4 & 7 \end{bmatrix}
    • From the second equation: A2B=[5432]A - 2B = \begin{bmatrix} -5 & 4 \\ 3 & 2 \end{bmatrix}
  2. Find the determinant of AB1AB^{-1}:

    • We will use the relationship: det(AB1)=det(A)det(B)\text{det}(AB^{-1}) = \frac{\text{det}(A)}{\text{det}(B)}

I will first solve the system to find AA and BB, then calculate the determinants.

Let me proceed with the solution.The matrices AA and BB are:

A=[5323534],B=[5353231]A = \begin{bmatrix} -\frac{5}{3} & \frac{2}{3} \\ \frac{5}{3} & 4 \end{bmatrix}, \quad B = \begin{bmatrix} \frac{5}{3} & -\frac{5}{3} \\ -\frac{2}{3} & 1 \end{bmatrix}

The determinants are:

det(A)=709,det(B)=59\text{det}(A) = -\frac{70}{9}, \quad \text{det}(B) = \frac{5}{9}

Finally, the determinant of AB1AB^{-1} is:

det(AB1)=det(A)det(B)=14\text{det}(AB^{-1}) = \frac{\text{det}(A)}{\text{det}(B)} = -14

Would you like further explanation or have any questions?

Here are 5 related questions to expand your understanding:

  1. What does the inverse of a matrix represent geometrically?
  2. How is the determinant of a product of matrices related to the individual determinants?
  3. What happens when the determinant of a matrix is zero?
  4. How does matrix multiplication affect the size of matrices?
  5. Why is the determinant of the inverse matrix the reciprocal of the original determinant?

Tip: Inverting matrices with determinants close to zero can lead to numerical instability, so always check the determinant before inverting!

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Math Problem Analysis

Mathematical Concepts

Matrices
Determinants
Matrix Inversion
Algebraic Equations

Formulas

det(AB^-1) = det(A) / det(B)
Matrix Determinant Formula for 2x2: det(A) = ad - bc

Theorems

Determinant Theorem
Inverse of a Matrix Theorem

Suitable Grade Level

Grades 11-12