Bonjour
x - y = 4
2 x + 5 y = - 6
x - y = 4 ⇔ x = 4 + y
2 ( 4 + y ) + 5 y = - 6
8 + 2 y + 5 y = - 6
7 y = - 6 - 8
7 y = - 14
y = - 2
x - ( - 2 ) = 4
x + 2 = 4
x = 2
S ( 2 : - 2 )
3 a + b = 3
5 a + 2 b = - 24
3 a + b = 3 ⇔ b = 3 - 3 a
3 a + 2 ( 3 - 3 a ) = - 24
3 a + 6 - 6 a = - 24
- 3 a = - 24 - 6 = - 30
- 3 a = - 30
a = 10
3*10 + b = 3
b = 3 - 30 = - 27
S ( 3 : - 27 )
