Math Problem Statement

Solve for the matrix X in the equation: [3, 9; -1, -8]X + [2, 9; 5, -8] = [4, 3; -1, 1]X.

Solution

The problem you're working on is solving for the matrix XX, where the equation is:

[3918]X+[2958]=[4311]X\begin{bmatrix} 3 & 9 \\ -1 & -8 \end{bmatrix} X + \begin{bmatrix} 2 & 9 \\ 5 & -8 \end{bmatrix} = \begin{bmatrix} 4 & 3 \\ -1 & 1 \end{bmatrix} X

Step-by-Step Solution

  1. Rearrange the equation so that all terms involving XX are on one side: [3918]X[4311]X=[2958]\begin{bmatrix} 3 & 9 \\ -1 & -8 \end{bmatrix} X - \begin{bmatrix} 4 & 3 \\ -1 & 1 \end{bmatrix} X = - \begin{bmatrix} 2 & 9 \\ 5 & -8 \end{bmatrix}

  2. Factor out the matrix XX on the left-hand side: ([3918][4311])X=[2958]\left( \begin{bmatrix} 3 & 9 \\ -1 & -8 \end{bmatrix} - \begin{bmatrix} 4 & 3 \\ -1 & 1 \end{bmatrix} \right) X = - \begin{bmatrix} 2 & 9 \\ 5 & -8 \end{bmatrix}

  3. Subtract the two matrices on the left-hand side: [34931(1)81]=[1609]\begin{bmatrix} 3 - 4 & 9 - 3 \\ -1 - (-1) & -8 - 1 \end{bmatrix} = \begin{bmatrix} -1 & 6 \\ 0 & -9 \end{bmatrix} So now we have: [1609]X=[2958]\begin{bmatrix} -1 & 6 \\ 0 & -9 \end{bmatrix} X = - \begin{bmatrix} 2 & 9 \\ 5 & -8 \end{bmatrix}

  4. Multiply both sides by the inverse of the matrix [1609]\begin{bmatrix} -1 & 6 \\ 0 & -9 \end{bmatrix} to solve for XX.

The inverse of [1609]\begin{bmatrix} -1 & 6 \\ 0 & -9 \end{bmatrix} is calculated as: Inverse=1determinant×adjugate\text{Inverse} = \frac{1}{\text{determinant}} \times \text{adjugate} The determinant of [1609]\begin{bmatrix} -1 & 6 \\ 0 & -9 \end{bmatrix} is (1)(9)(6)(0)=9(-1)(-9) - (6)(0) = 9.

The adjugate (or transpose of the cofactor matrix) is: [9601]\begin{bmatrix} -9 & -6 \\ 0 & -1 \end{bmatrix}

So the inverse is: 19[9609]=[123013]\frac{1}{9} \begin{bmatrix} -9 & -6 \\ 0 & -9 \end{bmatrix} = \begin{bmatrix} -1 & -\frac{2}{3} \\ 0 & -\frac{1}{3} \end{bmatrix}

  1. Multiply the inverse with the right-hand side matrix to find XX.

If you want detailed steps on how to perform the multiplication, let me know!


Do you want further details or clarification on any step?

Here are 5 related questions for further practice:

  1. How do you calculate the inverse of a 2x2 matrix?
  2. What are the properties of matrix multiplication?
  3. Can all matrices be inverted? If not, why?
  4. What is the determinant of a matrix, and how is it used?
  5. How do you factor out a matrix in an equation?

Tip: When dealing with matrices, always check if the determinant is non-zero before attempting to calculate the inverse.

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Math Problem Analysis

Mathematical Concepts

Matrix Algebra
Matrix Inversion
Matrix Subtraction
Systems of Equations

Formulas

Matrix equation rearrangement: AX + B = CX
Inverse of a 2x2 matrix: A^-1 = 1/det(A) * adjugate(A)

Theorems

Matrix Inversion Theorem
Determinant Calculation

Suitable Grade Level

College Level or Advanced High School