Qui pourrais me faire mais 2dernier exercice de mon dm niveau 4eme voici les photos

Exercice 22
A= 2/3 + 3/5 = 2X5/3X5 + 4X3/5X3 = 10/15 + 12/15 = 22/14
B= 1/6 - 5/7 = 1X7/6X7 - 5X6/7X6 = 7/42 - 30/42 = 23/42
C= -3/2 + 7/9 = -3X9/2X9 + 7X2/9X2 = -27/18 + 14/18 = -13/18

7/24-5/8
= 7/24-5*3/8*3
= 7/24 -15/24
= -8/24
= -4*2/2*12
= -4/12
= -2*2/2*6
= -2/6
= -2*1/3*2
= -1/3

-5/18-11/6
= -5/18 -11*3/6*3
= -5/18 -33/18
= -38/18
= -19*2/9*2
= -19/9

11/45- -5/9
= 11/45 - -5*5/9*5
= 11/45- -25/15
= 36/45
= 9*4/9*5
= 4/5

-8/7- -10/21
= -8*3/7*3- -10/21
= -24/21- -10/21
= -14/21
= -7*2/7*3
= -2/3