matrix invers

for 2x2

\[ A^{-1} = \frac{1}{(a \cdot d) - (b \cdot c)} \begin{bmatrix} d & -b & \newline -c & a \end{bmatrix}\]

for 3x3 \[ A^{-1} = \frac{1}{\det A} \text{adj } A \]

sequence for 3x3 matrix

• search minor matrices (tutup angka)
• then calculate cofactor (plus minus)
• matrix adjoin (transpose of cofactor matrix)