Bonjour,
A = 3 √20 + √45
A = 3√(4 × 5) + √(9 × 5)
A = 3√(2² × 5) + √(3² × 5)
A = 3 × 2 × √5 + 3 √5
A = 6√5 + 3√5
A = 9√5
B = √180 – 3 √5
B = √(36 × 5) - 3√5
B = √(6² × 5) - 3√5
B = 6√5 - 3√5
B = 3 √5
A × B = 9 × √5 × 3 × √5 = 27 × (√5)² = 27 × 5 = 135 qui est un entier
A/B = (9√5)/(3√5) = 9/3 = 3 qui est un entier
