Réponse :
A = 3(-3x+5)-7 = -4(x+8)
=3*(-3x)+3*5-7=-4x-4*8
=-9x+15-7=-4x-32
=-9x+8=-4x-32
=-5x+8=-32
=-5x=-40
=x=8
B = 3x²-9=0
=3x²=9
=x²=3
=x=[tex]\sqrt{3}[/tex]
C = x²-3x-40=0
=x²-3x=40
=x²-2x=40+x
=x²/x-2x=40+x/x
=x-2x=40+1
=x-2x=41
=x=41
Bonne continuation ! :)