Réponse :
Soit x² + 2x = Y
E = Y² + 6Y - 27 = 0 => Y² + 9Y - 3Y - 27 = 0 => Y(Y+9) - 3(Y+9) = 0
=> (Y+9)(Y-3) = 0 => Y+9 = 0 => Y = -9
=> Y - 3 = 0 => Y = 3
x² + 2x = -9 => x² + 2x + 9 = 0 delta = 0 :=> pas de solution
x² + 2x = 3 => x² + 2x -3 = 0 => x² + 3x - x - 3 = 0 => x(x+3) -(x+3) = 0
=> (x+3)(x-1) = 0 => x = -3 ou x = 1
Bonne journée
Explications étape par étape :
