Réponses

2014-04-21T21:08:29+02:00
Expliquer pourquoi le couple (-5;3) est la solution du système
 x + 2y = 1
2x + 3y = -1


x = -2y + 1
2 (-2y + 1) + 3y + 1 = 0
- 4y + 2 + 3y + 1 = 0
-y = - 2 - 1
- y = - 3
y = 3

x + 2 * 3 - 1 = 0
x + 6 - 1 = 0
x = - 6 + 1
x = -5

Les solutions de l'équation sont : (-5 ; 3)
2014-04-21T21:15:39+02:00
X + 2y = 1
x = 1 -2y

 2x + 3y = -1
2 (1-2y) +3y =-1
2-4y +3y =-1
-y = -1-2
-y = -3
y =3

si y = 3 donc
x = 1 -2y
x = 1-2*3 = 1-6 = -5

donc couple = ( -5; 3)