bonsoir
1. 7
7 x 3 /7 = 21/7
21 /7 + 5 = 21/7 + 35/7 = 56/7
56/7 : 1 /5 = 56/7 x 5 = 280/7 = 40
2) 28/15
28/15 x 3 /7 = 84/105 = 4/ 5 (simplifié par 21 )
4/5 + 5 = 4/5 + 25/5 = 29/5
29/5 : 1 /5 = 29/5 x 5 = 145/5 = 29
3 ) x
3 x /7
3 x /7 + 5
( 3 x /7 + 5 ) : 1/5
= ( 3 x /7 + 5 ) x 5
= 15 x /7 + 25
15 x /7 + 25 = 0
15 x /7 = - 25
15 x /7 = - 175/7
15 x = - 175
x = - 175/15 = - 35/3
il faut choisir - 35 /3
- 35 /3 x 3 /7 = - 105/21
- 105/21 + 5 = - 105/21 + 105/21 = 0
