diketahui sistem persmaaan linear x+y+z=-12,2x+y-z=-11 dan x-2y-z=6 nilai xyz

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jawab

x+ y + z =  - 12
2x + y - z = -11 ..(+)
3x + 2y = -33 ...(i)

x + y + z = -12
x -2y - z = 6....(+)
2x - y = - 6 ..(ii)

(i) dan (ii)
3x  + 2y = - 33
2x - y = - 6...|X2

3x + 2y = - 33
4x - 2y = - 12....|(+)
7x = - 21
x = - 3

2x - y = - 6
y = 2x + 6
y = 2(-3) + 6
y = 0

x+ y + z = -12
-3 + 0+ z = -12
z = - 9

xyz = 0