HHHHHHHHHHHHHHHHHHHHHHHaiix +ai2x2a21x + a22x, =b2a2D=a21a22顶国下质
+ = + = . , 2 1 1 2 2 2 2 1 1 1 1 2 2 1 a x a x b a x a x b , 21 22 11 12 a a a a D =
HHHHHHHHHHHHHHHHHHHHHHHbraiix + ai2x2b,一a21x +a22x2bia12D,=b2a22br,a11xi + a12x2中ba21Xi + a22x2一Pla2D=a21a22上页国下质
+ = + = . , 2 1 1 2 2 2 2 1 1 1 1 2 2 1 a x a x b a x a x b , 2 22 1 12 1 b a b a D = + = + = . , 2 1 1 2 2 2 2 1 1 1 1 2 2 1 a x a x b a x a x b , 21 22 11 12 a a a a D =
HHHHHHHHHHHHHHHHHHHHHHHbraiix + ai2x2a21xi + a22x2ba12D, =b2a22山a1rxi + ai2x2a21Xi + a22x2bian1D2 =b2a21正页国下质
+ = + = . , 2 1 1 2 2 2 2 1 1 1 1 2 2 1 a x a x b a x a x b , 2 22 1 12 1 b a b a D = + = + = . , 2 1 1 2 2 2 2 1 1 1 1 2 2 1 a x a x b a x a x b . 21 2 11 1 2 a b a b D =
HHHHHHHHHHHHHHHHHHHHHH则二元线性方程组的解为bia12b,a11b2Da22D2b,a21Xi=X2Dana12Dan1a12a21a22a21a22注意分母都为原方程组的系数行列式上页回下页
则二元线性方程组的解为 , 2 1 2 2 1 1 1 2 2 2 2 1 1 2 1 1 a a a a b a b a D D x = = 注意 分母都为原方程组的系数行列式. . 2 1 2 2 1 1 1 2 2 1 2 1 1 1 2 2 a a a a a b a b D D x = =
HHHHHHHHHHHHHHHHHHHHHHH例1求解二元线性方程组3x - 2x, = 12,2x + x, = 1.3-2解= 3-(-4) = 7± 0,D=2112-2312= -21,D == 14,D2 =21114D2-21D1-3.= 2, X2Xi=一D7D7上页下页返回
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 = − − =