Bonjour Elcia,
1- Supprimer les parenthèses,puis reduire chaque expression:
A=(2x-3x^2+5y)-(y^2+2x)
A = 2x - 3x^2 + 5y - y^2 - 2x
A = -3x^2 - y^2 + 5y
B=-(4x-3y+3)-(3x+4z)
B = -4x + 3y - 3 - 3x - 4z
B = -7x + 3y - 4z - 3
C=-(4x-5x^2+3y-4y^2)+2-4x^2+(2x^2-3)-4(-x^2-y^2)
C = -4x + 5x^2 - 3y + 4y^2 + 2 - 4x^2 + 2x^2 - 3 + 4x^2 + 4y^2
C = 7x^2 + 8y^2 - 4x - 3y - 1
D=-(x+1)-(-x-1)
D = -x - 1 + x + 1
D = 0