●サラスの方法 (Sarrus's method, Rule of Sarrus)
+ + + − − − \ \ \ / / / A B C A B C \ \ \ / / / *−−−−−−−−−−−−−−−−−−* *−−−−−−−−−−−−−−−−−−* \ \ \ / / / D E F D E F \ \ \ / / / *−−−−−−−−−−−−−−−−−−* *−−−−−−−−−−−−−−−−−−* \ \ \ / / / G H I G H I \ \ \ / / / Δ= +BFG +CDH +AEI -CEG -AFH -BDI