Réponse :
bonjour
A(x) = x² + 6 x + 9
A(x) = ( x + 3 )²
B (x) = x² + 2 x + 15
Δ = 4 - 4 ( 1 *15) = 4 - 60 = - 46 = Ф
C (x) = x² + 18 x + 77
Δ = 324 - 4 ( 77) = 16
x 1 = ( - 18 + 4 ) / 2 = - 14/2 = - 7
x 2 = ( - 18 - 4 )/2 = - 22 /2 = - 11
x² + 18 x + 77 = ( x - 7) ( x - 11 )
D (x) = 2 x² - 7 x + 8
Δ = 49 - 4 ( 2 *8) = 49 - 64 = - 15 = Ф
Explications étape par étape