、二阶行列式的引入 用消元法解二元线性方程组 X +aux. 111 ,tax=b 211 2 2 1221+a 12“222 229 (2)Xa12:a12a1x1+a22x2=b2a2, 两式相减消去x2,得用消元法解二元线性方程组    + = + = . , 21 1 22 2 2 11 1 12 2 1 a x a x b a x a x b (1) (2) (1) : a22 , a11a22 x1 + a12a22 x2 = b1a22 (2) : a12 , a12a21x1 + a12a22 x2 = b2a12 两式相减消去 x2，得 一、二阶行列式的引入