bonjour
je les résous algébriquement
3 x + y = 5
- 2 x + y = - 5
y = 5 - 3 x
- 2 x + 5 - 3 x = - 5
- 5 x = - 5 - 5
- 5 x = - 10
x = 2
3 x + y = 5
6 + y = 5
y = 5 - 6
y = - 1
2 x + y = 3
- 2 x + 4 y = - 6
5 y = - 3
y = - 3/15 = - 1/5
2 x - 1/5 = 3
10 x - 1 = 15
10 x = 16
x = 1.6
- x + y = 1
2 x + y = 2
y = 1 + x
2 x + 1 + x = 2
3 x = 1
x = 1/3
2 x + y = 2
2/3 + y = 2
2/3 + 3 y = 6
3 y = 4
y = 4/3
- 2 x + 2 y = 10
2 x - y = - 8
y = 2
- 2 x + 4 = 10
- 2 x = 6
x = - 3
