Réponse :
bonsoir
( √6)² + 6 ² = 6 + 36 = 42
3√10 x 2 √5 = 6 √50 = 6 √2 x √25 = 30 √2
( √2 + √3)² = 2 + 2√6 + 3 = 5 + 2 √6 (identité remarquable)
3√2 + 5 √8 = 3 √2 + 5 √2 x √4 = 3 √2 + 10 √2 = 13√2
A = 3 x² + 2 x + 4
si x = - √2
A = 3 ( - √2)² + 2 ( - √2) + 4
= 6 - 2 √2 + 4 = 10 - 2 √2