Sagot :
A=15x^2+25x+12x+20-(12x^2-42x+6x-21)=3x^2+73x+41
B=-12x^2+15x+32x-40+12x^2-4x-18x+6=25x-34
C=10x^2-40x+12x-48-12-6x-20x-10x^2=-54x-60
B=-12x^2+15x+32x-40+12x^2-4x-18x+6=25x-34
C=10x^2-40x+12x-48-12-6x-20x-10x^2=-54x-60