X+y+2z=9 X-4y+z=1 2x+y+z=5

X+y+2z=9
2x+y+z=5
_______ _
-x + z = 4

x-4y+z=1
2x+y+z=5

x. - 4y + z. = 1
8x + 4y + 4z = 20
_______________ +
9x + 5z = 21

-x + z = 4
9x + 5z = 21

-5x + 5z = 20
9x + 5z = 21
___________ _
-14x = -1
x = 1/14

-x + z = 4
-1/14 + z = 4
z = 4 1/14
z = 57/14

x + y + 2z = 9
1/14 + 57/14 + 2z = 9
2z = 9 - 1/14 - 57/14
2z = 34/7
z = 17/7

X+y+2z=9 ....(1)
X-4y+z=1 ....(2)
2x+y+z=5 ....(3)

ELIMINASI (1) dan (2)
x + y + 2z = 9
x - 4y + z = 1
------------------- --
5y + z = 8 ....(4)

ELIMINASI (2) dan (3)
x - 4y + z = 1 ....(×2)
2x + y + z = 5
..
2x - 8y + 2z = 2
2x + y + z = 5
---------------------- --
9y + z = - 3 ....(5)

ELIMINASI (4) dan (5)
5y + z = 8
9y + z = - 3
---------------- --
- 4y = 11
y = - 11/4

5y + z = 8
5(-11/4) + z = 8
- 55/4 + z = 8
z = 8 + 55/4
z = 32/4 + 55/4
z = 87/4

x + y + 2z = 9
x + (-11/4) + 2(87/4) = 9
x + (-11/4 + 174/4) = 9
x + 163/4 = 9
x = 9 - 163/4
x = 36/4 - 163/4
x = - 127/4

jadi x = - 127/4 , y = - 11/4 , z = 87/4