Réponses

2014-04-24T13:49:32+02:00
Donner les résultats sous forme de fraction irréductible

A = 3/2 - 5/2 x 7/15 - 9/28 x 14/3
A = 3/2 - 5 x 7 - 9 x 14
             2 x 15  28 x 3
A = 3/2 - 35/30 - 126/84
A = 3 x 1260 / 2 x 1260 - 35 x 84 / 30 x 84 - 126 x 30 / 84 x 30
A = 3780/2520 - 2940/2520 - 3780/2520
A = -2940/2520
A = 420 x - 7 / 420 x 6
A = - 7/6

B = 2/3 (7/4 - 1/3) + 7/15 (5/21 - 5/7)
B = 2/3 (7 x 3 / 4 x 3 - 1 x 4 / 3 x 4) + 7/15 (5/21 - 5 x 3 / 7 x 3)
B = 2/3 (21/12 - 4/12) + 7/15 ( 5/21 - 15/21)
B = 2/3 x 17/12 + 7/15 x -10/21
B = 2 x 17 + 7 x -10
       3 x 12  15 x 21
B = 34/36 - 70/315
B = 34 x 315 / 36 x 315 - 70 x 36 / 315 x 36
B = 10710/11340 - 2520/11340
B = 8200/11340
B = 20 x 410 / 20 x 567
B = 410/567

C = 7/2 - 1/3 - 3/4
       3/2 - 2 - 2/31
C = 7 x 6 / 2 x 6 - 1 x 4 / 3 x 4 - 3 x 3 / 4 x 3
       3 x 31 / 2 x 31 - 2 x 62 / 1 x 62 - 2 x 2 / 31 x 2
C = 42/12 - 4/12 - 9/12
     93/62 - 124/62 - 4/62
C = 29/12
     -35/62
C = 29/12 : -35/62
C = 29/12 x -62/35
C = 29 x -62
       12 x 35
C = -1798/420
C = 2 x - 899 / 2 x 210
C = -899/210