Subjects algebra

Matrix Equation 049A6D

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Matrix Equation 049A6D


1. Zadatak: Riješiti matričnu jednadžbu $$X \cdot A - 2B = X$$ gdje su $$A = \begin{bmatrix}2 & -1 \\ 5 & 3 \end{bmatrix}, \quad B = \begin{bmatrix}0 & -1 \\ 3 & 5 \end{bmatrix}.$$ 2. Prvo preuredimo jednadžbu da izrazimo $X$: $$X \cdot A - X = 2B \implies X(A - I) = 2B,$$ gdje je $I$ jedinična matrica dimenzija 2x2. 3. Izračunajmo $A - I$: $$A - I = \begin{bmatrix}2 & -1 \\ 5 & 3 \end{bmatrix} - \begin{bmatrix}1 & 0 \\ 0 & 1 \end{bmatrix} = \begin{bmatrix}1 & -1 \\ 5 & 2 \end{bmatrix}.$$ 4. Da bismo našli $X$, pomnožimo obje strane s inverzom matrice $(A - I)$: $$X = 2B (A - I)^{-1}.$$ 5. Izračunajmo inverz matrice $(A - I)$: Determinanta: $$\det(A - I) = 1 \cdot 2 - (-1) \cdot 5 = 2 + 5 = 7.$$ Inverz: $$ (A - I)^{-1} = \frac{1}{7} \begin{bmatrix}2 & 1 \\ -5 & 1 \end{bmatrix}.$$ 6. Izračunajmo $2B$: $$2B = 2 \cdot \begin{bmatrix}0 & -1 \\ 3 & 5 \end{bmatrix} = \begin{bmatrix}0 & -2 \\ 6 & 10 \end{bmatrix}.$$ 7. Pomnožimo $2B$ s $(A - I)^{-1}$: $$X = \begin{bmatrix}0 & -2 \\ 6 & 10 \end{bmatrix} \cdot \frac{1}{7} \begin{bmatrix}2 & 1 \\ -5 & 1 \end{bmatrix} = \frac{1}{7} \begin{bmatrix}0 \cdot 2 + (-2) \cdot (-5) & 0 \cdot 1 + (-2) \cdot 1 \\ 6 \cdot 2 + 10 \cdot (-5) & 6 \cdot 1 + 10 \cdot 1 \end{bmatrix} = \frac{1}{7} \begin{bmatrix}10 & -2 \\ 12 - 50 & 16 \end{bmatrix} = \frac{1}{7} \begin{bmatrix}10 & -2 \\ -38 & 16 \end{bmatrix}.$$ 8. Konačno: $$X = \begin{bmatrix} \frac{10}{7} & -\frac{2}{7} \\ -\frac{38}{7} & \frac{16}{7} \end{bmatrix}.$$