ex 8 et 9 niveau 4e sur le produi en ecriture fractionnaire

8)
A = - 1/2 x 3/4 x 5/7
A = - 3/8 x 5/7
A = - 15/56

B = - 5/2 x 13/ - 3 x - 2/7
B = 65/6 x - 2/7
B = - 130/42
B = 2 x - 65 / 2 x 21
B = - 65/21

C = - 1/11 x 13/-5 x 3/-2
C = 13/55 x - 3/2
C = - 39/110

D = - 11/20 x - 2/10 x 5/-3
D = 22/200 x 5/-3
D = - 110/600
D = 10 x - 11 / 10 x 60
D = - 11/60

E = 15/4 x 16/-3 x - 5/2
E = - 240/12 x - 5/2
E = 1200/24
E = 24 x 50 / 24 x 1
E = 24/1
E = 24

F = - 1/2 x 3/-4 x - 5/6 x 2/-9
F = 3/8 x 10/54
F = 30/432
F = 6 x 5 / 6 x 75
F = 5/72

9)
a) 3/7 x 21 = 63/7 = 7 x 9 / 7 x 1 = 9

b) 11/10 x 25 = 275/10 = 5 x 55 / 5 x 2 = 55/2

c) 27/30 x 125 = 3375/30 = 15 x 225 / 15 x 2 = 225/2

d) 25/7 x 0,4 = 10/7

e) - 10 x 14/25 = - 140/25 = 5 x - 28 / 5 x 5 = - 28/5

f) 46 x - 0,5/23 = - 23/23 = - 1