x-4y+z=-3 2x-y+z=18 x-y-z=12

问题描述:

x-4y+z=-3 2x-y+z=18 x-y-z=12

x-4y+z=-3 (1)2x-y+z=18 (2)x-y-z=12 (3)(2)-(1)得:x+3y=21 (4)(1)+(2)得:2x-5y=9 (5)(4)×2-(5)得:11y=33y=3代入(4)得:x=21-9=12代入(1)得:z=-3-12+12=-3所以,方程组的解是:x=12;y=3;z=-3...