Réponses

2014-03-27T19:04:57+01:00
1) 9x + 7y = 52
2) 9x + 4y = 30
Soustraire 2) de 1)
3y = 22
y = 22/3
remplacer y par sa valeur dans 1) ou 2)
9x + 7*(22/3) = 52
9x + 154/3 = 52
9x = 52 - 154/3
9x = 156/3 - 154/3
9x = 2/3
x = (2/3)/9 = 2/27

7x + 4y = 6
5x + 2y = 0
5x=-2y
x=-2y/5
-14y/5+4y =6
6y=30
y = 30/6 =5
5x + 10 =0
5x = -10
x=-10/5
x=-2