Math Problem Statement

Suppose that A, B, and X are invertible square matrices of the same size. Solve for X in terms of A and B: (4B^{-1}X)^{-1} = ((3A)^{-1}B^{-1})BA^3

Solution

Let's analyze the problem and solve for XX step by step.

The equation given is:

(4B1X)1=((3A)1B1)BA3(4B^{-1} X)^{-1} = \left( (3A)^{-1} B^{-1} \right) B A^3

Step 1: Inverse of both sides

We can start by taking the inverse of both sides to remove the outer inverse on the left-hand side. Using the property that the inverse of an inverse is the original matrix:

4B1X=[((3A)1B1)BA3]14B^{-1} X = \left[ \left( (3A)^{-1} B^{-1} \right) B A^3 \right]^{-1}

Step 2: Simplify the right-hand side

We simplify the product on the right-hand side first. Notice that B1B=IB^{-1} B = I (where II is the identity matrix), so:

((3A)1B1)BA3=(3A)1A3\left( (3A)^{-1} B^{-1} \right) B A^3 = (3A)^{-1} A^3

Now, simplify (3A)1A3(3A)^{-1} A^3. This can be broken down further by using the property (AB)1=B1A1(AB)^{-1} = B^{-1} A^{-1}, and knowing that A1A=IA^{-1} A = I:

(3A)1A3=13A1A3=13A2(3A)^{-1} A^3 = \frac{1}{3} A^{-1} A^3 = \frac{1}{3} A^2

Thus, the equation becomes:

4B1X=(13A2)14B^{-1} X = \left( \frac{1}{3} A^2 \right)^{-1}

Step 3: Inverse of the right-hand side

Now, take the inverse of 13A2\frac{1}{3} A^2. The inverse of a scalar multiplied by a matrix is given by (cA)1=1cA1\left( c A \right)^{-1} = \frac{1}{c} A^{-1}, so:

(13A2)1=3A2\left( \frac{1}{3} A^2 \right)^{-1} = 3 A^{-2}

Now the equation is:

4B1X=3A24B^{-1} X = 3 A^{-2}

Step 4: Solve for XX

Multiply both sides of the equation by BB to eliminate B1B^{-1} from the left-hand side:

4X=3BA24X = 3 B A^{-2}

Finally, divide both sides by 4:

X=34BA2X = \frac{3}{4} B A^{-2}

Final Answer:

X=34BA2X = \frac{3}{4} B A^{-2}

Would you like further clarification on any part of this process or have additional questions?


Here are 5 related questions to expand your understanding:

  1. What is the significance of the inverse of a matrix in solving matrix equations?
  2. How can you verify if a matrix is invertible?
  3. What properties of matrix multiplication and inversion are crucial for solving this problem?
  4. Can you derive XX if the matrices were not square?
  5. How does scalar multiplication work with matrices?

Tip: Always ensure that the dimensions of matrices are compatible when multiplying or inverting them.

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Math Problem Analysis

Mathematical Concepts

Matrix Algebra
Inverse Matrices
Matrix Equations

Formulas

(AB)^{-1} = B^{-1}A^{-1}
A^{-1}A = I

Theorems

Properties of Matrix Inversion
Inverse of Product of Matrices

Suitable Grade Level

Undergraduate level (Linear Algebra)