tentukan himpunan penyelesaian dari sistem persamaan berikut a. 3x-y+z=-5 b. x-2y+z=3 c. 2x+y+z=-2

3x - y + z = -5
x - 2y + z = 3
--------------------(-)
2x + y = -8 ... pers 1

x - 2y + z = 3
2x + y + z = -2
---------------------(-)
-x - 3y = 5 .... pers 2

pers 1 & 2
2x + y = -8 |×1|
-x - 3y = 5. |×2|
2x + y = -8
-2x - 6y = 10
-------------------(+)
-5y = 2
y = - 2/5

- x - 3y = 5
- x - 3(-2/5) = 5
- x + 6/5 = 5
-x = 5 - 6/5
------------------(×5)
-5x = 25 - 6
-5x = 19
x = - 19/5

x - 2y + z = 3
- 19/5 - 2(-2/5) + z = 3
-------------------------------(×5)
-19 +4 + z = 15
z = 15 + 15
z = 30