Help Me N•4et5 mercii

Bonjour,

4)
a) 1/4 + 1/2 
= 1/4 + 1 x 2 / 2 x 2
= 1/4 + 2/4
= 3/4

b) - 2/ - 5 + 7/5
= 2/5 + 7/5
= 9/5

c) 1 - 8/7
= 1 x 7 / 1 x 7 - 8/7
= 7/7 - 8/7
= - 1/7

d) - 7/15 - 2/3
= - 7/15 - 2 x 5 / 3 x 5
= - 7/15 - 10/15
= - 17/15

5)
a) 5/12 - 3/4
= 5/12 - 3 x 3 / 4 x 3
= 5/12 - 9/12
= - 4/12
= 4 x - 1 / 4 x 3
= - 1/3

b) 2/3 + - 4/15 
= 2/3 - 4/15
= 2 x 5 / 3 x 5 - 4/15
= 10/15 - 4/15
= 6/15
= 3 x 2 / 3 x 5
= 2/5

c) - 7/24 + 5/8
= - 7/24 + 5 x 3 / 8 x 3
= - 7/24 + 15/24
= 8/24 
= 8 x 1 / 8 x 3
= 1/3

d) 3/20 - 9/10
= 3/20 - 9 x 2 / 10 x 2
= 3/20 - 18/20
= - 15/20 
= 5 x - 3 / 5 x 4
= - 3/4

4°
a)3 sur 4
b)9 sur 5
c)-1 sur 7
d)-17 sur 15
5°
a)-1 sur 3
b)14 sur 15
c)1 sur 3
d)-3 sur 4