Math Problem Statement

Solve for the matrix X in the equation: \( \begin{pmatrix} 3 & 2 \\ -5 & -3 \end{pmatrix} \cdot X = \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix} \).

Solution

The question involves solving for the matrix XX in the equation:

(3253)X=(1234).\begin{pmatrix} 3 & 2 \\ -5 & -3 \end{pmatrix} \cdot X = \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix}.

Step-by-Step Solution:

  1. Rewrite the equation: The equation is: AX=B,A \cdot X = B, where:

    B = \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix}.$$ To find $$X$$, multiply both sides by $$A^{-1}$$ (the inverse of $$A$$) from the left: $$X = A^{-1} \cdot B.$$
  2. Find the inverse of AA: The inverse of a 2×22 \times 2 matrix is calculated as: A1=1det(A)adj(A),A^{-1} = \frac{1}{\text{det}(A)} \cdot \text{adj}(A), where:

    • det(A)=(3)(3)(2)(5)=9+10=1\text{det}(A) = (3)(-3) - (2)(-5) = -9 + 10 = 1,
    • adj(A)=(3253)\text{adj}(A) = \begin{pmatrix} -3 & -2 \\ 5 & 3 \end{pmatrix} (swap the diagonal elements and change the sign of the off-diagonal elements).

    Thus:

    = \begin{pmatrix} -3 & -2 \\ 5 & 3 \end{pmatrix}.$$
  3. Calculate XX: Multiply A1A^{-1} by BB: X=A1B=(3253)(1234).X = A^{-1} \cdot B = \begin{pmatrix} -3 & -2 \\ 5 & 3 \end{pmatrix} \cdot \begin{pmatrix} 1 & 2 \\ 3 & 4 \end{pmatrix}.

    Perform the matrix multiplication:

    X_{12} = (-3)(2) + (-2)(4) = -6 - 8 = -14,$$ $$X_{21} = (5)(1) + (3)(3) = 5 + 9 = 14, \quad X_{22} = (5)(2) + (3)(4) = 10 + 12 = 22.$$ Therefore: $$X = \begin{pmatrix} -9 & -14 \\ 14 & 22 \end{pmatrix}.$$

Final Answer:

X=(9141422).X = \begin{pmatrix} -9 & -14 \\ 14 & 22 \end{pmatrix}.

Let me know if you want further explanation or a verification step!

Related Questions:

  1. How do you calculate the determinant of a matrix?
  2. What is the adjugate matrix and how is it used in finding inverses?
  3. How do you verify if a matrix is invertible?
  4. Can this process be extended to larger matrices, and if so, how?
  5. What are the practical applications of solving matrix equations?

Tip: Always check the determinant of a matrix before attempting to find its inverse; a determinant of zero means the matrix is not invertible.

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Math Problem Analysis

Mathematical Concepts

Matrix Algebra
Matrix Inverse
Matrix Multiplication

Formulas

Matrix equation: A \cdot X = B
Inverse of a 2x2 matrix: A^{-1} = \frac{1}{\text{det}(A)} \cdot \text{adj}(A)
Matrix multiplication

Theorems

Inverse of a matrix
Properties of matrix multiplication

Suitable Grade Level

Grades 11-12