Salut,A(x)= (x-4)(3x+1)-(4-5x)(2x+3)=(3x²+x-12x-4)-(8x+12-10x²-15x)=3x²+x-12x-4-8x-12+10x²+15x=13x²-4x-16 . B(x)=(2x-3)²-(x+4)²=(2x²-2(2x)(3)+9)-(x²+8x+16)=4x²-12x+9-x²-8x-16=3x²-20x-7. C(x)=3(2x-1)²-2(1+x)²=3(4x²-4x+1)-2(1+2x+x²)=12x²-12x+3-2-4x-2x²= 10x²-16x+1. J'espère t'avoir aidé.