Répondre :
A=3y²+12y+2y+8
=3y²+14y+8
B=6y²-10y+3y-5
=6y²-7y-5
C=12y²+28y-6y-14
=12y²+22y-14
D=y²-2y-3y+6
=y²-5y+6
E=(16y²+56y-8y-28)-(15y²-45y+18y-54)
=16y²+56y-8y-28-15y²+27y+54
=y²+75y+26
voila, voila !
=3y²+14y+8
B=6y²-10y+3y-5
=6y²-7y-5
C=12y²+28y-6y-14
=12y²+22y-14
D=y²-2y-3y+6
=y²-5y+6
E=(16y²+56y-8y-28)-(15y²-45y+18y-54)
=16y²+56y-8y-28-15y²+27y+54
=y²+75y+26
voila, voila !