Réponse :
A= 3x + 9 - 4x + 20 = - x + 29
B= 10x + 15 - 24x -30
C= - 2x + 6 - 3x - 12 = - 5x - 6
D= -8x -12 +15x +20 = 7x +6
E= 3x² -6x + 3 -4x +12 = 3x² -10x +15
F= -6x² -8x -15x² +10x = -21x² +2x
G= 8x² +12x +16 +15x² -20x = 23x² -8x +16
H= 10x² +6x +15x +9 = 10x² +21x +9
I= 21x² -9x -35x +15 = 21x² -44x +15
J= 81x² +9x -9x -1 + 81x² -1
K= 16x² -24x -20x +30 +6x² +6x -2x -2 = 22x² -20x -2
