Question

resolva o sistema:x+y+z=4
2x+y-z=-5
x-2y+3z=9

Answer 1

Olá...

x+y+z= 4
2x+y-z= -5
x-2y+3z= 9
-------------------

x+y+z= 4
(x= 4-y-z)

2x+y-z= -5
2(4-y-z)+y-z= -5
8-2y-2z+y-z= -5
8-y-3z= -5
-y= -5 -8 +3z (-1)
y= 5+8-3z
(y= 13-3z)

x-2y+3z= 9
1(4-y-z)-2.(13-3z)+3z= 9
4-1y-z-26+6z+3z= 9
4-1.(13-3z)-z-26+9z= 9
4-13+3z-z-26+9z= 9
-9+2z+9z-26= 9
-35+11z= 9
11z= 9+35
11z= 44
z= 44/11
[z= 4]

y= 13-3z
y= 13-3.4
y= 13-12
[y= 1]

x= 4-y-z
x= 4-1-4
x= 4-5
[x= -1 ]

Comprovando os valores:

x+y+z= 4

-1+1+4= 4
4= 4

Espero ter ajudado!!!