三元一次方程组x-2y=-9 3x-y+z=4 y=2x-7 y-z=3 2x+3y-z=12 5x+3y+2z=2 2z+x=47 x+y+z=6 x+4z=4

1）由①③=> x-2（2x-7)=-9 => x-4x+14=-9 => -3x=-23 => x=23/3 => y=46/3-7=25/3∴ z=4-3x+y=4-69/3+25/3=-32/3∴ x=23/3 ；y=25/3 ；z=-32/32)由① y=3+z 代入②③=> 2x+3(3+z)-z=12 5x+3(3+z)+2z=2 => 2x+2z=3 5...