Réponse :

Bonsoir,

A = 197 x 21

= 197 x (17 + 4)

= 197 x 17 + 197 x 4

= 3349 + 788

= 4137 .

D = 197 x 51

= 197 x (17 + 17 + 17)

=197 x 17 + 197 x 17 + 197 x 17

= 3349 + 3349 + 3349

= 10047 .

B = 197 x 13

= 197 x (17 - 4)

= 197 x 17 - 197 x 4

= 3349 - 788

= 2561 .

E = 197 x 9

= 197 x (13 - 4)

= 197 x 12 - 197 x 4

= 2561 - 788

= 1773 .

C = 197 x 34

= 197 x (17 + 17)

= 197 x 17 + 197 x 17

= 3349 + 3349

= 6698 .

F = 197 x 42

= 197 x (51 - 9)

= 197 x 51 - 197 x 9

= 10047 - 1773

= 8274 .

b.

197 x 8 = 197 x (4 + 4) = 197 x 4 + 197 x 4

            = 788 + 788 = 1576 .

197 x 5 = 197 x (4 + 1) = 197 x 4 + 197 x 1  

           = 788 + 197 = 985 .

197 x 18 = 197 x (17 + 1)

             = 197 x 17 + 197 x 1

           = 3349 + 197 = 3546 .

En espérant t'avoir aidé.