bonsoir

pour le 3 tu prends ta calculatrice

A = 5 √5 ( 3 - √3 ) = 15 √5 - 5 √15

B = 3 √6 - 9 √15

c = 4 + 12 √5 + 45 = 49 + 12 √5

D = 5 - 6 √10 + 18 = 23 - 6 √ 10

E = 2 - 6 √10 + 45 = 47 - 6 √10

F = 8 - 27 = - 19

G = 2 √49 - √7 = 14 - √7

H = 3 √5 ( 10 - 8 √5 - 15 √5 + 12 √25 )

= 3 √5 ( 10 - 23 √5 + 60 )

= 3 √5 ( 70 - 23 √5 )

= 210 √5 - 345

= - 135 √ 5

2 / √7 = 2 ( √7 ) / ( √7 )²

= 2 √7 / 7