Réponses

2014-09-04T19:04:26+02:00
1). -3/4 - 2/5 = - 3 x 5 / 4 x 5 - 2 x 4 / 5 x 4 = - 15/20 - 8/20 = - 23/20

2) 15/49 × 28/35 = 420/1715 = 35 x 12 / 35 x 49 = 12/49

3) 2/3 × 9/4 × 8/10 = 18/12 x 8/10 = 144/120 = 24 x 6 / 24 x 5 = 6/5

4) 8/21 ÷ 4/7 = 8/21 x 7/4  = 56/84 = 28 x 2 / 28 x 3 = 2/3

5). -12/9 ÷  - 28/27 = - 12/9 x - 27/28 = 324/252 = 36 x 9 / 36 x 7 = 9/7

  • Utilisateur Brainly
2014-09-04T19:10:27+02:00
- 3/4 - 2/5
= - 15/20 - 8/20
= - 23/20

15/49 × 28/35 
= (15 * 28)/(49 * 35)
= 420/1715
= 12/49

 2/3 × 9/4 × 8/10
= (2*9*8)/(3*4*10)
= 144/120
= 6/5

8/21 ÷ 4/7
= 8/21 * 7/4
= 56/84
= 2/3

 
- 12/9 ÷ -28/27
= 12/9 * 27/28
= 324/252
= 9/7