Nilai x+y+z jika diketahui 2x+y-3z=3, x-y+5z=-2, 2x+2y-z=-1 adalah

2x + y – 3z = 3
x – y + 5z = -2
2x + 2y – z = -1

2x + y – 3z = 3
x – y + 5z = -2
~~~~~~~~~~~~ +
3x + 2z = 1 ••••• A

x – y + 5z = -2 ( kali 2 )
↓
2x – 2y + 10z = -4
2x + 2y – z = -1
~~~~~~~~~~~~~~ +
4x + 9z = -5 ••••• B

4A → 12x + 8z = 4
3B → 12x + 27z = -15
~~~~~~~~~~~~~~~~~~ –
-19z = 19
z = 19/-19
→ z = -1

A••• 3x + 2z = 1
3x + 2(-1) = 1
3x = 2 + 1
x = 3/3
→ x = 1

x – y + 5z = -2
1 – y + 5(-1) = -2
-y + 1 – 5 = -2
-y = -2 + 4
→ y = -2

→ x + y + z

= 1 -2 -1

= -2