Bonsoir de l’aide svp

Bonsoir,

a)
x - 5y = -11
-3x + 4y = 11

x = -11 + 5y
-3 (-11 + 5y) + 4y = 11

x = -11 + 5y
33 - 15y + 4y = 11

x = -11 + 5y
33 - 11y = 11

x = -11 + 5y
22 = 11y

x = -11 + 5 * 2
2 = y

x = -1
y = 2


b)
-6x + y = 15
5x - 7y = -31

y = 15 + 6x
5x - 7 (15 + 6x) = -31

y = 15 + 6x
5x - 105 - 42x = -31

y = 15 + 6x
-37x = 74

y = 15 + 6 * (-2)
x = -2

y = 3
x = -2


je te laisse calculer les deux derniers :)