解下列方程组: (1)(3x-y+z=10 (x+2y-z=6 (x+y+z=12 (2)(2x+4y+3z=9(3x-2y+5z=11(5x-6y+7z=13

来源:学生作业帮助网 编辑:六六作业网 时间:2024/11/22 20:55:35
解下列方程组:(1)(3x-y+z=10(x+2y-z=6(x+y+z=12(2)(2x+4y+3z=9(3x-2y+5z=11(5x-6y+7z=13解下列方程组:(1)(3x-y+z=10(x+2

解下列方程组: (1)(3x-y+z=10 (x+2y-z=6 (x+y+z=12 (2)(2x+4y+3z=9(3x-2y+5z=11(5x-6y+7z=13
解下列方程组: (1)(3x-y+z=10 (x+2y-z=6 (x+y+z=12 (2)(2x+4y+3z=9(3x-2y+5z=11(5x-6y+7z=13

解下列方程组: (1)(3x-y+z=10 (x+2y-z=6 (x+y+z=12 (2)(2x+4y+3z=9(3x-2y+5z=11(5x-6y+7z=13
(1)
3x-y+z=10 (1)
x+2y-z=6 (2)
x+y+z=12 (3)
由(1)+(2)得
4x+y=16 (4)
由(1)-(3)得
2x-2y=-2
x-y=-1 (5)
由(4)+(5)得
5x=15
x=3
y=4
z=5
(2)
2x+4y+3z=9 (1)
3x-2y+5z=11 (2)
5x-6y+7z=13 (3)
由(1)+(2)*2得
8x+13z=31 (4)
由(1)*3+(3)*2得
16x+23z=53 (5)
由(4)*2-(5)得
3z=9
z=3
x=-1
y=1/2