bonjour svp 4 equation du second degré a resoudre j'y comprend rien = au carré a) x + 4x - 12 = 0 b) x + 8x + 16 = 0 c) x + 4x + 5 = 0 d) x - 4x - 2 = 0

x² + 4x - 12 = 0

Δ = b²-4ac
Δ = 4²-4*1*(-12)
Δ = 16+48
Δ = 64

√Δ = √64 = 8

x₁ = (-b-√Δ)/2a = (-4-8)/2*1 = -12/2 = -6
x₂ = (-b+√Δ)/2a = (-4+8)/2*1 = 4/2 = 2

x² + 8x + 16 = 0

Δ = 8²-4*1*16
Δ = 64 - 64
Δ = 0

x₀ = -b/2a = -8/2*1 = -8/2 = -4

x² + 4x + 5 = 0 

Δ = 4²-4*1*5
Δ = 16 - 20
Δ = -4
Δ < 0

Pas de solution réelle 

x² - 4x - 2 = 0

Δ = (-4)²-4*1*(-2)
Δ = 16+8
Δ = 24

x₁ = (-b-√Δ)/2a = (4-√24)/2
x₂ = (-b+√Δ)/2a = (4+√24)/2