Bonjour
1) x² = 5
x² - 5 = 0
a = 1 ; b = 0 ; c = -5
Calcul du discriminant Δ :
Δ = b² - 4ac
Δ = 0 - 4 * 1 * (-5)
Δ = 20
Δ > 0 donc le polynome admet deux racines
x1 = (-b - √Δ)/2a = -2√5/2 = -√5
x2 = (-b + √Δ)/2a = 2√5/2 = √5
b) x² = -1
x² + 1 = 0
a = 1 ; b = 0 ; c = 1
Calcul du dicriminant Δ :
Δ = b² - 4ac
Δ = - 4 * 1 * 1
Δ = -4
Δ < 0 donc le polynome n'admet aucune racine
c) x² = 0
x = 0