Réponse :
bonjour
donc 1 et 2 et niveau collège, pas lycée
a = 9/2 et b = 6 /5
S = 9/2 - 6/5
S = 45/10 - 12/10 = 33 /10
S = 9/2 * 6/5 = 56/10
S = 9/2 x 5/6 = 45/12 = 15/4
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A = 5/7 - 21/6 x 10/14
A = 5/7 - 210/84
A = 5/7 - 5/2
A = 10/14 - 35/14 = - 25/14
B = 8/5 - 8/5 x 20/32
B = 8/5 - 160/160
B = 8/5 - 1
B = 8/5 - 5/5 = 3/5
Explications étape par étape :
