L’exercice 3 svp je ni arrive pas. Merci d’avance

Bonjour

Exos 3

♧1.
B = 15x - 21
B = 3(5x-7)

♧2.
C = (5x-7)²(x-9)-(15x-21)(4x+11)
C = (5x-7)² (x-9) - 3(5x-7)(4x+11)
C = (5x-7)[(5x-7)(x-9)-3(4x+11)]
C = (5x-7)(5x²-64x+30)

Voilà ^^