Explications étape par étape:
A= 9x-63+6x-30= 15x-93
B= 6x-24-20x+12= -14x-12
C= -21x-24+25x-10x-20= -6x-44
D= 12x²+8x+30x+20-1-2x= 12x²+36x+19
E= 12x+(-15x²)-21x+20x+28= -15x²+11x+28
F= -12x²+8x+48x-32+16x²-15x+24x-20=4x²+65x-52
G= 24x²+16x-18x-12-12x²+10x+24x-20= 12x²+32x-32
