Nilai x+y+z dari persamaan berikutx+y-z=-3x+2y+z=72x+y+z=4
Jawaban:
x + y – z = -3
x + 2y + z = 7
2x + y + z = 4
• eliminasi pers. 1 dan 2
x + y – z = -3
x + 2y + z = 7
___________ +
2x + 3y = 4 — pers. 4
• eliminasi pers. 1 dan 3
x + y – z = -3
2x + y + z = 4
____________ +
3x + 2y = 1 — pers. 5
• eliminasi pers. 4 dan 5
2x + 3y = 4
3x + 2y = 1
_________ _
6x + 9y = 12 — x3
6x + 4y = 2 — x2
__________ _
5y = 10
y = 2
• subtitusi nilai y
3x + 2y = 1
3x + 2(2) = 1
3x = -3
x = -1
• subtitusi x dan y
x + y – z = -3
(-1) + 2 – z = -3
-z = -4
z = 4
• nilai x + y + z
= (-1) + 2 + 4