SVP URGENT !!!!!! POUR DEMAIN VIIITE REPONSE EXPLIQUER SVP

1)- 
A=5a+3a+7b+6b=8a+13b
B=7x+5y-3x-12y=4x-7y
C=6x²+12+3x²+5x+2x=9x²+7x+12
D=9x²-12x+7-15-3x+4x²

2)-
E=-(5a+2b)=-5a-2b
F=50-(-50+10x)=50+50-10x=100-10x
G=(3a+2b)+(4a+b)=3a+2b+4a+b=7a+3b
H=-(11x+5)+(17x-6)=-11x-5+17x-6=6x-11