A+2b+2c=5,3a-b+2c=-4 dan 2a+b-c=15 tentukan hp dan persamaan linear 3 variabel

a + 2b + 2c = 5
3a - b + 2c = - 4
------------------------(-)
- 2a + 3b = 9

a + 2b + 2c = 5
2a + b - c = 15 |×2
a + 2b + 2c = 5
4a + 2b - 2c = 30
-------------------------(+)
5a + 4b = 35

- 2a + 3b = 9 |×5
5a + 4b = 35 |×2
- 10a + 15b = 45
10a + 8b = 70
---------------------(+)
23b = 115
b = 5

- 2a + 3b = 9
- 2a + 3(5) = 9
- 2a = 9 - 15
- 2a = - 6
a = 3

a + 2b + 2c = 5
3 + 2(5) + 2c = 5
3 + 10 + 2c = 5
2c = 5 - 13
2c = - 8
c = - 4

hp = {3,5,-4}