Réponse :
Bonjour
Explications étape par étape
Exercice 1
A = (2x +5)(4x +8)
A = 8x² +16x +20x +40
A = 8x² +36x +40
B = (7x +4)(8 -7x)
B = +32x -49x² +32 -28x
B = -49x² +4x +32
C = (x -3)(7x -4)
C = 7x² -4x -21x +12
C = 7x² -25x +12
D = (-2x +8)(4 -x)
D = -8x +2x² +32 -8x
D = -16x +2x² +32
Exercice 2
E = (9 -2x)(-2x +6) + (4x +1)(3 -2x)
E = (-18x +54 +4x² -12x) + (+12x -8x² +3 -2x)
E = -30x +54 +4x² -8x² +10x +3
E = -4x² -20x +57
F = (5 +2x)(3 -4x) - (1 -3x)(5x +6)
F = (+15 -20x +6x -8x²) - ( +5x +6 -15x² -18x)
F = (-8x² -14x +15) - ( -15x² -13x +6)
F = -8x² -14x +15 +15x² +13x -6
F = +7x² -x +9
G = 4 ( 5x -3) + (2x -1)(x +4)
G = 20x -12 +2x² +8x -x -4
G = +2x² +27x -16
H = 3x - (4x +1) + (-x +2)(5 -x)
H = 3x -4x -1 + (-5x +x² +10 -2x)
H = -x -1 +x² -7x +10
H = -8x +x² +9
