行列式{xy2,123,233}中元素y的代数余子式是()

Question

行列式{x y 2,1 2 3,2 3 3}中元素y的代数余子式是( )

Answer 1

x y 2
1 2 3
2 3 3
A12 = (-1)^(1+2)*
1 3
2 3
= - (3-6)
= 3.