Réponse :
Par combinaison
[tex]\left \{ {{2x - 2y = 4} \atop {6x - 4y = 28}} \right.[/tex]
[tex]\left \{ {{2x * (-2) - 2y * (-2) = 4 * (-2) } \atop {6x - 4y = 28}} \right.[/tex]
[tex]\left \{ {{-4x +4y = -8 } \atop {6x - 4y = 28}} \right.[/tex]
-4x + 4y + 6x - 4y = -8 +28
-4x + 6x = 2x = 20
x = 20/2 = 10
2x - 2y = 4
2 × 10 - 2y = 20 - 2y = 4
- 2y = 4 - 20 = -16
y = -16/-2 = 8
