sistem persamaan 2x + 2y = 10 dan 4x -2y = 8. maka nilai 3x + 3y adalah

Eliminasi persamaan (1) dan (2) :
2x + 2y = 10
4x - 2y = 8
..........................+
6x = 18
x = 3

Subsitusi x ke salah satu persamaan :
2x + 2y = 10
2(3) + 2y = 10
6 + 2y = 10
2y = 10 - 6
2y = 4
y = 2

3x + 3y
=3 (3) + 3 (2)
= 9 + 6
= 15

2x +2y=10| *4
4x - 2y=8 |*2
8x +8y=40
8x - 4y=16
....................-
0 +12y=24
y= 24/12 = 2

2x + 2y =10 |*1
4x - 2y = 8 | *-1

2x + 2y = 10
-4x +2y = -8
......................-
6x + 0 = 18
x = 18/6 =3

3x + 3y =
3(3) + 3(2) =
9+6 =15

2x +2y=10| *4
4x - 2y=8 |*2
8x +8y=40
8x - 4y=16
....................-
0 +12y=24
y= 24/12 = 2

2x + 2y =10 |*1
4x - 2y = 8 | *-1

2x + 2y = 10
-4x +2y = -8
......................-
6x + 0 = 18
x = 18/6 =3

3x + 3y =
3(3) + 3(2) =
9+6 =15