Répondre :
(x²+7x-3)-(3x-5x²-6=
= x^2+5x^2+7x-3x-3+6
=6x^2+4x+3
3y²-(3y-9)-(2y²-4y-5)
=3y^2-2y^2-3y+4y+9+5
= y^2+y+14
VOila, bon courage.
1) (x^2+7x-3)-(3x-5x^2-6)
= x^2+7x-3-3x+5x^2+6
= 6x^2+4x+3
2) 3y^2-(3y-9)-(2y^2-4y-5)
=3y^2-3y+9-2y^2+4y+5
=y^2+y+14