Réponses

2014-06-11T12:26:29+02:00
Bonjour

A= 2/5+3/7= 14/35 + 15/35 = 29/35
B=1/4+ -3/2= 1/4 - 6/4 = - 5/4
C=7/-5+ -4/3= - 21/15 - 20/15 = - 41/15
D= 5/6-1/6+2/7=
35/42 - 7/42 + 12/42 = 47/42 - 7/42 = 40/42 = 20/21

Meilleure réponse !
2014-06-11T14:02:52+02:00
A = 2/5 + 3/7
A = 2 x 7 / 5 x 7 + 3 x 5 / 7 x 5
A = 14/35 + 15/35
A = 29/35

B = 1/4 + -3/2
B = 1/4 - 3 x 2 / 2 x 2
B = 1/4 - 6/4
B = - 5/4

C = 7/-5 + -4/3
C = 7 x 3 / - 5 x 3  - 4 x 5 / 3 x 5
C = - 21/15 - 20/15
C = - 41/15

D = 5/6 - 1/6 + 2/7
D = 5 x 7 / 6 x 7 - 1 x 7 / 6 x 7 + 2 x 6 / 7 x 6
D = 35/42 - 7/42 + 12/42
D = 40/42
D = 2 x 20 / 2 x 21
D = 20/21