Réponses

2014-02-09T19:12:30+01:00
Exercice 1 : 

A= -2/5 +3/7
A= -14/35 + 15/35
A= 1/35

B= 5/6 - 1/6*7
B= 4/6*7
B= 28/6
B= 14/3

C= 2-2/3*5/7
C= 2 - 10/21
C=42/21 - 10/21
C= 32/21

D= 5/9 + 7 
D= 5/9 + 63/9
D= 68/9

E= (1+2/7) + ( 1-2/7)
E= ( 7/7+2/7)+(7/7-2/7)
E= ( 9/7 ) + 5/7
E= 14/7
E= 2

F= 3/8 - 3/14*7/6
F= 3/8 - 21/84
F= 63/168 - 42/168
F= 21/168
F= 1/8

G= (2-1/3) - 20/9
G= ( 6/3 - 1/3) - 20/9
G= 5/3 - 20/9
G= 15/9 - 20/9
G= - 5/9

H= 1-1/3+5/3-28/35
H= 1 + 4/3 - 28/35
H= 3/3+4/3 - 28/35
H= 7/3 - 28/35
H= 245/105 - 84/105
H= 161/105
H= 23/15

Exercice 2 : 

A= 3(a+7)
A= 3a + 21

B= -3(10x-7)
B= - 30x + 21 

C= 8n + 2(n-1)+4
C= 8n + 2n - 2+ 4
C= 10n + 2 

D=(7a +6)+(9a+14)
D=16a + 20

E=- (7t+5) + 3(2t+6)
E= - 7t - 5 + 6t+ 12
E= -t+7

F= 3(4t-8) -(2t-5)
F= 12t -24 - 2t + 5
F= 10t - 19
2014-02-09T19:18:24+01:00
A = -2/5 + 3/ 7                                                  E = (1+ 2/7) / (1-2/7)
A = -14/35 + 15/35                                            E = (7/7 +2/7) / (7/7 - 2/7)
A = 1/35                                                            E = 9/7 /  5/7
                                                                          E = 9/7 x 7/5
                                                                          E = 63/35 = 9/7
B = 5/6 - 1/6 x 7
B = 5/6 + 7/6                                                     F = 3/8 - 3/14 x 7/6
B = -2/6                                                              F = 3/8 - 21/84
                                                                           F = 3/8 x 84/21
C = 2 - 2/3 x 5/7                                                 F = 252/168 = 3/2
C =2 -10/21
C= 42/21 - 10/21                                             G = (2-1/3) / 20/9
C= 32/21                                                          G = (6/3 - 1/3 ) x 9/20
                                                                         G = 5/3x9/20
D = 5/9 /  7                                                        G = 45 / 60 = 3/4
D = 5/9 x 1/7
D = 5/63