例1求解二元线性方程组 3x1-2x2=12 2x1+x2=1 解 3-2 D=2 =3-(-4)=7≠0, 11=14,D,=3 D、12 2 2 =-21, 21 D114 D =2,12=s-21 3. D7 D 7 上页例 1  + = − = 2 1. 3 2 12, 1 2 1 2 x x x x 求解二元线性方程组 解 2 1 3 − 2 D = = 3 − ( − 4 ) = 7  0 , 1 1 12 2 1 − D = = 14 , 2 1 3 12 D 2 = = −21 , DD x 1  1 = 2 , 7 14 = = DD x 2 2 = 3. 7 21 = − − =