按照图示步骤求解
5x+4y+z=0 ①
3x+y-4z=11 ②
x+y+z=-2 ③
(1)-(3)
4x+3y=2 (4)
4(3)+(2)
7x+5y=3 (5)
3(5)-5(4)
x=-1
from (5)
7x+5y=2
-7+5y=2
y=9/5
from (3)
x+y+z=-2
-1+9/5 +z =-2
4/5 +z = -2
z= -14/5
(x,y,z)=(-1,9/5, -14/5)