4x-y=2 2y+z=3 2x-z=1 maka nilai 2y+2z=

4x - y = 2 ............. (1)
2y + z = 3 ............ (2)
2x - z = 1 .............. (3)

Masukan persamaan (1) ke (2)
4x - y = 2
-y = 2 - 4x
y = 4x -2 ....... (1)

2y + z = 3 ......... (2)
2 ( 4x - 2 ) + z = 3
8x - 4 + z = 3
8x + z = 3 +4
8x + z = 7 ......... (4)

Eliminasi persamaan (3) dan (4)
2x - z = 1
8x + z = 7
___________ +
10x = 8
x = 0.8

4x - y = 2
4 ( 0.8) -y = 2
3.2 -y = 2
-y = 2 - 3.2
-y = - 1.2
y = 1.2

2y + z = 3
2 (1.2) + z = 3
2.4 + z = 3
z = 3 - 2.4
z = 0.6

2y + 2z
= 2 ( 1.2 ) + 2 ( 0.6 )
= 2.4 + 1.2
= 3.6

Semoga membantu ^_^