tentukan nilai x dan y 1. 1/3(x+4)=1/2(y+1) 2x+3=3(y-2x)-8 2. x+2y=3x-y=7

1]

[1/3(x+4) = 1/2(y+1)](× 6)
2(x+4) = 3(y+1)
2x+8 = 3y+3
2x-3y = 3-8
2x-3y = -5

2x+3 = 3(y-2x)-8
2x+3 = 3y-6x-8
2x+6x-3y = -8-3
8x-3y = -11

2x-3y = -5
8x-3y = -11
----------------- -
-6x = 6
x = 6/-6
x = -1
2x-3y = -5
2(-1)-3y = -5
-2-3y = -5
3y = -2+5
3y = 3
y = 3/3
y = 1

jadi nilai x dan y adalah -1 dan 1

2]

x+2y = 3x-y = 7

x+2y = 7 (×1)
3x-y = 7 (×2)
x+2y = 7
6x-2y = 14
----------------- +
7x = 21
x = 21/7
x = 3

x+2y = 7
3+2y = 7
2y = 7-3
2y = 4
y = 4/2
y = 2

jadi nilai x dan y adalah 3 dan 2

Mapel : Matematika
Kelas : VIII SMP
Bab : SPLDV

Pembahasan :
1)

1/3(x + 4) = 1/2(y + 1)
2(x + 4) = 3(y + 1)
2x + 8 = 3y + 3
2x - 3y = -5

2x + 3 = 3(y - 2x) - 8
2x + 3 = 3y - 6x - 8
8x - 3y = -11

Eliminasi...
8x - 3y = -11
2x - 3y = -5
——————— (-)
6x = -6
x = -1

Substitusi...
2x - 3y = -5
2(-1) - 3y = -5
-3y = -5 + 2
-3y = -3
y = 1

Maka...
Nilai x dan y adalah -1 dan 1

————————————————
2)

x + 2y = 7 —» 3x + 6y = 21
3x - y = 7

Eliminasi...
3x + 6y = 21
3x - y = 7
——————— (-)
7y = 14
y = 2

Substitusi...
3x - y = 7
3x - 2 = 7
3x = 9
x = 3

Maka...
Nilai x dan y adalah 3 dan 2