Subjects linear algebra

Matrix Equation 1B4C67

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1. **Problem:** Given matrices \( A = \begin{bmatrix}4 & -6 \\ -2 & 3\end{bmatrix} \), \( B = \begin{bmatrix}7 & -8 \\ -4 & 5\end{bmatrix} \), and a 2x2 matrix \( X \), if \( AX = AB \), is \( X = B \)? 2. **Formula and rules:** The equation \( AX = AB \) implies \( A(X - B) = 0 \). 3. **Intermediate work:** Since \( A \) is a matrix, if \( A \) is invertible, then multiplying both sides by \( A^{-1} \) gives: $$ A^{-1}A(X - B) = A^{-1}0 \Rightarrow \cancel{A^{-1}A}(X - B) = 0 \Rightarrow X - B = 0 $$ 4. **Conclusion:** Therefore, if \( A \) is invertible, \( X = B \). 5. **Check invertibility of \( A \):** Calculate determinant: $$ \det(A) = 4 \times 3 - (-6) \times (-2) = 12 - 12 = 0 $$ Since \( \det(A) = 0 \), \( A \) is not invertible. 6. **Implication:** Because \( A \) is not invertible, we cannot conclude \( X = B \) from \( AX = AB \). **Final answer:** \( \boxed{\text{No, } X \neq B \text{ necessarily because } A \text{ is not invertible.}} \)