4x² + 3x + 2 = 0
Δ = b² - 4ac = 3² - 4 * 4 * 2 = 9 - 32 = -23
Δ < 0 → Pas de racine.
6x² - 12x = 0
Δ = b² - 4ac = (-12)² - 4 * 6 * 0 = 144
Δ > 0 → 2 racines
x1 = (-b - √Δ) / (2a)
= (-(-12) - √144) / (2 * 6)
= 0/12
= 0
x2 = (-b + √Δ) / (2a)
= (-(-12) + √144) / (2 * 6)
= (12 + 12) / 12
= 2
8x² + 8x + 2 = 0
Δ = b² - 4ac
= 8² - 4 * 8 * 2
= 64 - 64
= 0
Δ = 0 → 1 racine
x = -b/(2a) = -8/(2*8) = -1/2