Bonjour,
Exercice 4:
A=-(4x+1)+7+7x
A=-4x-4+7+7x
A=3x+3
B=-6+2x+(x+9)
B=-6+2x+x+9
B=3x+3
C=-(-8x+5)+4-3x
C=8x-5+4-3x
C=5x-1
Exercice5:
A=2x (7+4x)
A=14x+8x^2
B=(-3x+7)(-3)
B=9x^2-21
C=6x-4 (2x-8)
C=6x-8x+32
C=-2x+32
D=(3a-2)(4a-7)
D=12a^2-21a-8a+14
D=12a^2-29a+14
Bonne chance !