Bonsoir,
Factoriser:
x²/4+x+7= (x/2+1)² juste
(x-1)²-16(x-5)²= (x-1)²-4²(x-5)²= (x-1-4(x-5))(x-1+4(x-5))= (x-1-4x+20) (x-1+4x-20) = (-3x+19)(5x-21)= - (3x-19)(5x-21) corrigée.
x²-9= (x-3)(x+3) corrigée
2x(5x+4)+(5x+4)= (5x+4)(2x+1) corrigée
