Répondre :
A = (x+5)² - (2x-1)² + (3x + 4)² (x-1)
=(x+5-2x+1)(x+5+2x-1) +(3x + 4)² (x-1)
=(-x+6)(3x+4)+(3x + 4)² (x-1)
=(3x+4)(6-x+(3x+4)(x-1))
=(3x+4)(3x²+2)
=(x+5-2x+1)(x+5+2x-1) +(3x + 4)² (x-1)
=(-x+6)(3x+4)+(3x + 4)² (x-1)
=(3x+4)(6-x+(3x+4)(x-1))
=(3x+4)(3x²+2)