Réponse :
Bonjour
Exercice 1
A =x × (3 - x) = x×3 - x×x = -x² + 3x
B = a × (7 + b) = a×7 + a×b = 7a + ab
C = -5 × (3×x - 2) = -5×3x + (-5)×(-2) = -15x + 10
D = (2×t + 5) × 5 = 2t×5 + 5×5 = 10t + 25
E = 6×x × (1 - 3×x) = 6x×1 - 6x×3x = -18x² + 6x
F = (9×y + 5) × 6×y = 9y×6y + 5×6y = 54y² + 30y
Exercice 2
A = 5×x + 30 = 5×x + 5×6 = 5(x + 6)
B = 72 - 9×x = 9×8 - 9×x = 9(8 - x)
C = 42 + 4×x = 2×21 + 2×2×x = 2(21 + 2x)
D = 8×x - 36 = 4× 2x - 4×9 = 4(2x - 9)
Exercice 3
A = (x + 7) × (x + 3) = x×x + x×3 + 7×x + 7× 3 = x² + 10x + 21
