Question

Tolong bantu ya kak, bsk mau di kumpulin !

Answer 1

1. 4x - 7y = 1 |×7| → 28x - 49y = 7
7x + y = 15 |×4| → 28x + 4y = 60
__________-
-53y = -53
y = -53/-53
y = 1
Substitusi y = 1 kesalah satu persamaan
28x - 49y = 7
28x - 49(1) = 7
28x - 49 = 7
28x = 7 + 49
28x = 56
x = 56/28
x = 2
HP : {x = 2 dan y = 1}

2. x + 2y + 3z = 5 (persamaan 1)
3x + y + 2z = 6 (persamaan 2)
2x + 3y +z = 1 (persamaan 3)
Eliminasi persamaan 1 dan 2 :
x + 2y + 3z = 5 |×3|
3x + y + 2z = 6 |×1|
↓
3x + 6y + 9z = 15
3x + y + 2z = 6
______,______-
5y + 7z = 9 (persamaan 4)

Eliminasi persamaan 1 dan 3 :
x + 2y + 3z = 5 |×2|
2x + 3y + z = 1 |×1|
↓
2x + 4y + 6z = 10
2x + 3y + z = 1
_____,,_______-
y + 5z = 9 (persamaan 5)

Eliminasi persamaan 4 dan 5 :
5y + 7z = 9 (×1) = 5y + 7z = 9
y + 5z = 9 (×5) = 5y + 25z = 45
____________-
-18z = -36
z = -36/-18
z = 2
Substitusi z = 2 kepersamaan 4
5y + 7z = 9
5y + 7(2) = 9
5y + 14 = 9
5y = 9 - 14
5y = -5
y = -5/5
y = -1

Substitusi z = 2 dan y = -1 kepersamaan 1
x + 2y + 3z = 5
x + 2(-1) ) + 6 = 5
x - 2 + 6 = 5
x = 5 + 2 - 6
x = 1
HP : { x = 1 , y = -1 , z = 2 }