Aidez moi svp l'exercice 3

bonjour

a = - 2/21 et b = - 5/7

a/b = - 2/21 : - 5/7 = -2/21 * - 7/5 = 14/105

ab = - 2/21 * - 5/7 = 10/147

a + b = - 2/21 - 5/7 = - 2/21 - 15/21 = - 17/21

a - b = - 2/21 + 5/7 = - 2/21 + 15/21 = 13/21

a = 5/24 et b = - 35/18

a/b = 5/24 : - 35/18 = 5/24 * - 18/35 = - 90/840 = - 3/28

ab = 5/24 * - 35/18 = - 175/432 = 

a + b = 5/24 - 35/18 = 15/72 - 140/72 = - 125/72

a - b = 5/24 + 35/18 = 15/72 + 140/72 = 155/72