Bonjour
1)
85/15 = (5 x 14) / (5 x 3) = 14/3
11/12 = irréductible
12/15 = (3 x 4) / (3 x 5) = 4/5
49/59 = (7 x 7) / (7 x 8) = 7/8
54/81 = (27 x 2) / (27 x 3) = 2/3
303/273 = (3 x 101) / (3 x 91) = 101/91.
2)
8/16 = (8 x 1) / (8 x 2) = 1/2 donc oui 8/16 = 1/2
15/25 = (5 x 3) / (5 x 5) = 3/5 et 5/10 = (5 x 1) / (5 x 2) = 1/2
donc non car 3/5 ≠ 1/2
28/36 = (4 x 7) / (4 x 9) = 7/9 donc oui 28/36 = 7/9
42/56 = (14 x 3) / (14 x 4) = 3/4 = (3 x 2) / (4 x 2) = 6/8 donc oui 42/56 = 6/8.
3)
1/3 = (1 x 5) / (3 x 5) = 5/15
2/5 = (2 x 3) / (5 x 3) = 6/15
5/6 = (5 x 4) / (6 x 4) = 20/24
7/8 = (7 x 3) / (8 x 3) = 21/24
3/5 = (3 x 6) / (5 x 6) = 18/30
8/6 = (8 x 5) / (6 x 5) = 40/30
1/4
3/2 = (3 x 2) / (2 x 2) = 6/4
9/12
4/2 = (4 x 6) / (2 x 6) = 24/12
4/36
4/9 = (4 x 4) / (4 x 9) = 16/36.
