Réponse:

il faut utiliser la double distributivité :

( a + b) ( c + d) = (a×c) + (a×d) + (b×c) + (b×d)

Exemple A :

A = ( 2x+5) ( 4x+8)

A = (2x × 4x) + (2x × 8) + ( 5×4x) + (5×8)

A = 8x^2 + 16x + 20x + 40

A = 8x^2 + 36x + 40

J'espère t'avoir aidé et que tu réussiras les suivants :)

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