Nilai dari x, y, z dr persamaan linier, 3x + 6y = 33 ; 2x - 5z = -10 ; 8y + z = 28, maka nilai x + y - z =

3x + 6y = 33
x + 2y = 11
x = - 2y + 11

subtitusi
2x - 5z = - 10
2(-2y + 11 ) - 5z = - 10
- 4y + 22 - 5z = - 10
- 4y - 5z = - 10 - 22
- 4y - 5z = - 32

eliminasi
- 4y - 5z = - 32 |×2
8y + z = 28
maka
- 8y - 10z = - 64
8y + z = 28
-----------------------(+)
- 9z = - 36
z = 4

subtitusi
8y + z = 28
8y + 4 = 28
8y = 28 - 4
8y = 24
y = 3

subtitusi
2x - 5z = - 10
2x - 5(4) = - 10
2x - 20 = - 10
2x = - 10 + 20
2x = 10
x = 5

nilai x + y - z
= 5 + 3 - 4
= 4

3x - 6y = 33
2x - 5z = -10
8y + z = 28

3x+6y = 33 ... (x2)
2x-5z = -10 ... (x3)

6x+12y = 66
6x-15z = -30
___________-
12y-15z = 96

12y-15z = 96 ... (x1)
8y+z = 28 ... (x15)

12y-15z = 96
120y+15z = 420
_____________-
-108y = -324
y = 3

3x + 6y = 33
3x + 6(3) = 33
3x = 15
x = 5

2x - 5z = -10
2(5) - 5z = -10
-5z = -20
z = 4

nilai
x + y - z = 5 + 3 - 4 = 4

maaf kalau salah