metode substitusi dari x + 4y =14 dan 3x + 7y = 22

Bab Persamaan Linear
Matematika SMP Kelas VIII

x + 4y = 14
x = -4y + 14

3x + 7y = 22
3(-4y + 14) + 7y = 22
-12y + 42 + 7y = 22 
-5y = 22 - 42
y = -20 : (-5)
y = 4

x = -4y + 14
x = -4 . 4 + 14
x = -16 + 14
x = -2

(x, y) = (-2, 4)

x + 4y = 14 persamaan 1
3x + 7y = 22 persamaan 2

x + 4y = 14 persamaan 1
x = 14 - 4y
x = -4y + 14

substitusikan persamaan 1 ke persamaan 2:
3x + 7y = 22
3 (-4y + 14) + 7y = 22
-12y + 42 + 7y = 22
-5y = 22 - 42
y = -20 : (-5)
y = 4

masukkan nilai y-nya :
x = -4y + 14
x = -4 . 4 + 14
x = -16 + 14
x = -2

Hp {-2 , 4}