di tentukan nilai 3×+4y pada persamaan di bawah in 2×-6y=-8 7×+y=16

Sistem Persamaan Linear Dua Variabel
SMP Kelas VIII

2x - 6y = -8  Ix1I
7x + y = 16  Ix6I
---------------------------
2x - 6y = -8
42x + 6y = 96
--------------------------- +
44x = 88
x = 2

2x - 6y = -8
2(2) - 6y = -8
4 - 6y = -8
-6y = -8 - 4
-6y = -12
y = 2

3x + 4y = 3(2) + 4(2)
             = 6 + 8
             = 14

2x - 6y = - 8 .............. (÷ 2)
x - 3y = - 4
x = 3y - 4

Substitusi
7x + y = 16
7 (3y - 4) + y = 16
21y - 28 + y = 16
21y + y = 16 + 28
22y = 44
y = 44 / 22
y = 2

x = 3y - 4
x = 3 (2) - 4
x = 6 - 4
x = 2

3x + 4y = 3 (2) + 4 (2)
              = 6 + 8
3x + 4y = 14