Bonjour,
1)
a. - 6/11 = 6/- 11
b. - 5/- 7 = 5/7
c. 1/ - 6 = - 1/6
2)
a. 3/4 x 25 = 75/4
b. 5/3 x 8 = 40/3
c. 63/49 : 7 = 63/49 x 1/7 = 63/343
3)
a. 2/5 = (2 x 6) / (5 x 6) = 12/30
b. 0,4/- 7 = (0,4 x - 10) / (- 7 x - 10) = - 4/70
c. 60/28 = (60 : 4) / (28 : 4) = 15/7
d. 45/81 = (45 : 9) / (81 : 9) = 5/9.
4)
a. 2/-3 = - 2/3 --> Négatif
b. 7/8 --> Positif
c. - 4/- 7 = 4/7 --> Positif.