解方程组:{x+y-2z=-3① {2x+6y+z=2② {x+y+z=0③

题目

解方程组:{x+y-2z=-3① {2x+6y+z=2② {x+y+z=0③

答案

(2)×2+(1)
5x+13y=1 (4)
(2)-(3)
x+5y=2 (5)
(5)×5-(4)
25y-13y=10-1
12y=9
所以
y=3/4
x=2-5y=-7/4
z=-x-y=1