Bonjour j'ai un devoir maison à faire en mathe mais j'ai pas compris merci de m'aider. Merci pour votre réponse rapide. C'est le 3 et 4.

Bonjour,

3)

a. 3/4 : 5/7 = 3/4 x 7/5 = 21/12 = (3 x 7) / (3 x 4) = 7/4

b. 9/5 : 6/11 = 9/5 x 11/6 = 99/30 = (3 x 33) / (3 x 10) = 33/10

c. 15/8 : 6 = 15/8 x 1/6 = 15/48 = (3 x 15) / (3 x 16) = 15/16

d. 8/7 : 12 = 8/7 x 1/12 = 8/84 = (4 x 2) / (4 x 21) = 2/21.

4)

a. 3/7 + 15/7 x 3/2

= 3/7 + 45/14

= (3 x 2) / (7 x 2) + 45/14

= 6/14 + 45/14

= 51/14

b. 9/5 x (1/4 - 5/12)

= 9/5 x [(1 x 3) / (4 x 3) - 5/12]

= 9/5 x (3/12 - 5/12)

= 9/5 - 2/12

= (9 x 12) / (5 x 12) - (2 x 5) / (12 x 5)

= 108/60 - 10/60

= 98/60

= (2x 49) / (2 x 30)

= 49/30.

c. (3/8 + 7/5) : (9/4 - 5/3)

= [(3 x 5) / (8 x 5) + (7 x 8) / (5 x 8)] : [(9 x 3) / (4 x 3) - (5 x 4) / (3 x 4)]

= (15/40 + 56/40) : (24/12 - 20/12)

= 71/40 : 4/12

= 71/40 x 12/4

= 852/160

= (4 x 213) / (4 x 40)

= 213/40.