Tentukan himpunan penyelesaian dari persamaan 2x+3y-z=20, 3x+2y+z=20,x+4y+2z=15

2x + 3y - z= 20.. (1)
3x + 2y + z = 20 ...(2)
x + 4y +2z = 15 ...(3)


pers 1 dan 2
2x + 3y - z = 20 |-1 |
3x + 2y + z= 20 |1 |
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-2x - 3y + z = -20
3x + 2y + z = 20
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-5x - 5y = -40
5x + 5y = 40 ...(4)

pers 2 dan 3
3x + 2y + z = 20 | 2|
x + 4y + 2z = 15 |1 |
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6x + 4y + 2z = 40
x + 4y + 2z = 15
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5x = 25
x = 25/5
x = 5

5x + 5y = 40
5(5) + 5y = 40
25 + 5y = 40
5y = 40 - 25
5y = 15
y = 15/5
y = 3

x + 4y + 2z = 15
5 + 4(3) + 2z = 15
5 +12 + 2z = 15
17 +2z = 15
2z = 15 - 17
2z = -2
z = -2/2
z = -1