Bonjour,
Développer:
(x+3)²-(2x+1)(2x-1)= x²+3x+3x+9-(4x²+2x-2x-1)= x²+6x+9-4x²+1= -3x²+6x+10
(x-8)(3x+1)+(2x-7)²= 3x²-24x+x-8+4x²-14x-14x+49= 7x²-51x+41
7(x-2)(x-5)+(4x+3)²= 7(x²-2x-5x+10)+16x²+12x+12x+9= 7x²-49x+70+16x²+24x+9
= 23x²-25x+79
(1.2x-5)²-(2x-3)(2x+3)= 1.44x²-6x-6x+25-4x²+9= -2.56x²-12x+34
