Lycée 2nd Aidez moi si'il vous plait Substitution de : 2X + -3Y = 4 X + 4Y =13

Bonsoir,

2x - 3y = 4
x + 4y = 13

x = 13 - 4y
2 (13 - 4y) - 3y = 4
26 - 8y - 3y = 4
- 8y - 3y = 4 - 26
- 11y = - 22
y = 22/11
y = 2

x + 4y = 13
x + 4 (2) = 13
x + 8 = 13
x = 13 - 8
x = 5

Les solutions sont : (2 ; 5)

Bonsoir

♤ On a :

2X + -3Y = 4
X + 4Y =13

♤ Méthode par substitution :

2X + -3Y = 4
X = -4Y + 13

2(-4Y+13) - 3Y = 4
X = -4Y + 13

-8Y - 3Y + 26 = 4
X = -4Y + 13

-11Y = - 22
X = -4Y + 13

Y = 22/11 = 2
X = -4Y + 13

Y = 2
X = -4×2 + 13 = -8 + 13 = 5

X = 5
Y = 2

S={(5;2)}

Voilà ^^