SVP,AIDEZ MOI A FAIRE CA. URGENT MERCI BEAUCOUP

31)
A = 14/9 : 7/5
A = 14/9 x 5/7
A = 70/63
A = 7 x 10 / 7 x 9
A = 10/9

B = 3/ - 8 : 1/12
B = -3/8 x 12
B = -36/8
B = 4 x - 9 / 4 x 2
B = - 9/2

C = -15/10 : 12/-7
C = -15/10 x -7/12
C = 105/120
C = 15 x 7 / 15 x 8
C = 7/8

D = 14/15 : - 8/5
D = 14/15 x - 5/8
D = -70/120
D = 10 x - 7 / 10 x 12
D = - 7/12

32)
A = 7 : 4/3
A = 7 x 3/4
A = 21/4

B = 5/6 : (- 3)
B = 5/6 x -1/3
B = -5/18

C = - 12 : 6/5
C = - 12 x 5/6
C = - 60/6
C = 6 x - 10 / 6 x 1
C = - 10/1
C = - 10

33)
A = 5/7 : 2/3
A = 5/7 x 3/2
A = 15/14

B = 8/-15 : -4/3
B = -8/15 x - 3/4
B = 24/60
B = 12 x 2 / 12 x 5
B = 2/5

C = 5/9 : - 8
C = 5/9 x -1/8
C = -5/72

D = 5 : 9/-8
D = 5 x -8/9
D = -40/9

24)
A = - 13/6 + - 9/4
A = - 13/6 - 9/4
A = - 13 x 4 / 6 x 4 - 9 x 6 / 4 x 6
A = - 52/24 - 54/24
A = - 106/24
A = 2 x - 53 / 2 x 12
A = - 53/12

B = -7/15 + 11/6
B = - 7 x 2 / 15 x 2 + 11 x 5 / 6 x 5
B = - 14/30 + 55/30
B = 41/30

C = 7/8 + - 11/6
C = 7/8 - 11/6
C = 7 x 3 / 8 x 3 - 11 x 4 / 6 x 4
C = 21/21 - 44/24
C = - 23/24

44)
a) - 4/21 - (-9/7)
= - 4/21 + 9/7
= - 4/21 + 9 x 3 / 7 x 3
= - 4/21 + 27/21
= 23/21

b) 5/6 - (-1/7)
= 5/6 + 1/7
= 5 x 7 / 6 x 7 + 1 x 6 / 7 x 6
= 35/42 + 6/42
= 41/42

c) - 7/6 + 4/9
= - 7 x 3 / 6 x 3 + 4 x 2 / 9 x 2
= - 21/18 + 8/18
= - 13/18