Tolong Bantuin dong KAK, yang nomor 3 sama nomor 4...

3. 3x + 2y - z = 17
x - 3y + z = 1
x + y + 2z = 11

persamaan 1 & 2

3x + 2y - z = 17
x - 3y + z = 1
___________+
4x - y = 18 (1)

persamaan 1 & 3

3x + 2y - z = 17 |×2|
x + y + 2z = 11 |×1|

6x + 4y - 2z = 34
x + y + 2z = 11
_____________+
7x + 5y = 45 (2)

… (1) & … (2)

4x - y = 18 |×5|
7x + 5y = 45 |×1|

20x - 5y = 90
7x + 5y = 45
___________+
27x = 135
x = 5

substitusi x = 5

4x - y = 18
4.5 - y = 18
20 - y = 18
-y = 18 - 20
-y = -2
y = 2

substitusi x = 5, y = 2

x - 3y + z = 1
5 - 3.2 + z = 1
z = 1 - 5 + 6
z = 2


4. 3x - y + z = 10
2x + y - z = 10
4x - 3y - 2z = 15


persamaan 1 & 3

3x - y + z = 10 |×2|
4x - 3y - 2z = 15 |×1|

6x - 2y + 2z = 20
4x - 3y - 2z = 15
______________+
10x - 5y = 35 (1)

persamaan 2 & 3

2x + y - z = 10 |×2|
4x - 3y - 2z = 15 |×1|

4x + 2y - 2z = 20
4x - 3y - 2z = 15
_____________-
5y = 35
y = 7


substitusi y = 7

10x - 5y = 35
10x - 5.7 = 35
10x = 35 + 35
10x = 70
x = 7


substitusi x = 7, y = 7

3x - y + z = 10
3.7 - 7 + z = 10
z = 10 - 21 + 7
z = -4