{x+y-z=6,x-y+2z=-7,3x+2y+z=7解三元一次方程,

x+y-z=6 (1)x-y+2z=-7 (2)3x+2y+z=7 (3)分析:利用加减消去法,将未知数逐一消去(1) + (2):2x + z = -1 (3) (消去y)(1)*2:2x + 2y - 2z = 12 (4)(3) - (4):x + 3z = -5 (5) (消去y)(5)*2:2x + 6z = -10 (6)(6) - (3):5...