πŸ’‘ μˆ˜μ‹ μ‚½μž…

: https://www.notion.so/14-1f5fa00916414a43b4c7d77ee7dcf9ed

: https://jjycjnmath.tistory.com/117


행렬식

μ„±μ§ˆ

nμ°¨ 정사각행렬 $A = (a_{ij})$, $B = (b_{ij})$, $C = (c_{ij})$ 이고 $\alpha$ λŠ” μ‹€μˆ˜μ΄λ‹€.

LU μΈμˆ˜λΆ„ν•΄

ex) κ°€μ—­ν–‰λ ¬(=μ •μΉ™ν–‰λ ¬) $A = \begin{pmatrix} 1 & 3 & 7 \\ 2 & 6 & 8 \\ 0 & 4 & 3 \end{pmatrix}$ 을 행에 κ΄€ν•œ 사닀리꼴 ν–‰λ ¬ U와 κΈ°λ³Έν–‰λ ¬λ“€μ˜ 곱으둜 ν‘œμ‹œν•˜λ©΄,

$E_1 = \begin{pmatrix} 1 & 0 & 0 \\ -2 & 1 & 0 \\ 0 & 0 & 1 \end{pmatrix}$, $E_2 = \begin{pmatrix} 1 & 0 & 0 \\ 0 & 0 & 1 \\ 0 & 1 & 0 \end{pmatrix}$ μ΄λ―€λ‘œ

$U = E_2E_1A$ , $A = E_1^{-1} E_2^{-1} U$ 이 λœλ‹€.